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By the end of this article, you will understand the violent, two-stage process that likely formed Mars’ moons from a disk of molten rock and vapor, and why this means they are made of material from deep within the Martian mantle.

For decades, scientists have debated the origin of Phobos and Deimos. They look like captured asteroids, but their perfectly circular, equatorial orbits don’t add up. The ‘giant impact’ theory seemed promising, but the details were fuzzy. This Story changed when researchers ran a powerful supercomputer simulation. They created a virtual Mars and smashed a planetoid into it, using advanced physics to track not just where the debris went, but how it melted and vaporized. The simulation revealed a Salient Idea: a two-stage process. First, the impact created a hot, chaotic disk of meter-sized molten blobs. Second, these blobs, on highly eccentric orbits, collided at incredible speeds, grinding themselves down into the fine mixture of rock and dust that would eventually clump together to form the moons we see today.

Original Paper: ‘ON THE IMPACT ORIGIN OF PHOBOS AND DEIMOS I’

Our results will give useful information for planning a future sample return mission to Martian moons, such as JAXA’s MMX mission.
— Ryuki Hyodo et al., Research Paper Abstract

This formation process is NOT like the gentle clumping of asteroids in a cold disk. To Build a Fence around the concept: the key is extreme heat and violence. The initial disk was mostly liquid rock at ~2000 K. The droplets were about the size of a car, a size determined by the balance between the impact’s shear forces and the rock’s surface tension. The second stage is a ‘collisional cascade’. Because the blobs were on wildly different, elliptical orbits, they smashed into each other at 3-5 km/s. These hyper-velocity collisions were energetic enough to re-melt and shatter the blobs, grinding them down to particles 100 microns in size (the width of a human hair). Meanwhile, the small amount of rock vapor from the impact condensed into even finer, 0.1-micron dust, which would coat everything.

The building blocks of the Martian moons are expected to be a mixture of these different sized particles from meter-sized down to… 0.1µm-sized grains.
— Research Paper Abstract

A giant impact of this scale is a planetary catastrophe. It would have had a profound effect on early Mars’s atmosphere and magnetic field. The immense energy would have blown a significant portion of the atmosphere into space, while the vaporized rock would create a temporary, hot silicate atmosphere. Any hope of retaining a stable atmosphere—the kind needed to protect a planet from the solar wind and enable auroras—would depend on the strength and resilience of the planet’s magnetic field. This event serves as a stark reminder that a planet’s habitability is a delicate balance between its internal geological engine, which generates a protective magnetic shield, and the violent chaos of the cosmos.

This discovery wasn’t made with a telescope, but with a computational microscope. The team used a method called Smoothed Particle Hydrodynamics (SPH). They represented Mars and the impactor as millions of individual particles, then used a supercomputer to calculate the gravitational and thermodynamic forces on each one throughout the collision. The crucial Knowledge and Tools advancement was using the M-ANEOS equation of state, a sophisticated model that accurately predicts how materials like rock behave under extreme pressure and temperature—including when they melt or vaporize. This allowed them to see, for the first time, the true thermodynamic state of the moon-forming disk, transforming our understanding from a simple debris field to a dynamic, molten system.

Q: So, are Phobos and Deimos captured asteroids or not?
A: This research provides strong evidence against the captured asteroid theory. It shows how a giant impact could create the moons in their current orbits and predicts their composition is a mix of the impactor and deep Martian mantle—a key detail a sample return mission can test.

Q: Why were the initial blobs meter-sized?
A: That specific size is the result of a physical balancing act. The immense shear forces from the impact tried to tear the ejected liquid rock apart, while the material’s own surface tension tried to hold it together in droplets. The physics of this struggle naturally results in blobs about a meter across.

Q: Does this mean there are pieces of Mars’s core on its moons?
A: Not the core, but the mantle. The simulations show the impact was powerful enough to excavate and launch material from 50 to 150 km deep inside Mars. This means Phobos and Deimos could be natural archives of Mars’s deep, early interior.

By the end of this article, you will understand how scientists predict which exoplanets have magnetic fields strong enough to ‘shout’ their existence across space with radio waves, and why the hot Jupiter tau Boötis b is their #1 target.

Finding exoplanets is one thing, but understanding them is another. A huge missing piece of the puzzle is magnetism. Magnetic fields are invisible shields that protect a planet’s atmosphere. So, how do you find one light-years away? This Story is not about a single discovery, but a meticulous prediction. Researchers built a sophisticated numerical model to estimate the radio power of known exoplanets. They fed it data for over 1500 planets, simulating the interaction between each planet’s potential magnetosphere and its star’s wind. The model calculated the expected radio frequency and flux density, creating a ranked list of the ‘loudest’ potential targets in the sky. The Salient Idea: They’ve created a treasure map for radio astronomers, pointing them directly to the most promising candidates for the first-ever detection of an exoplanetary magnetic field.

Research Paper: ‘Radio prospects of extrasolar aurorae polaris as a probe of planetary magnetism’

Prospective extrasolar auroral emission detections will constrain the magnetic properties of exoplanets, allowing the assessment of the planets’ habitability…
— Asaf Kaya & Tansu Daylan, Researchers

When charged particles from a star’s wind slam into a planet’s magnetic field, they get funneled towards the poles. This is NOT like a satellite signal that is intentionally broadcast. Instead, the planet’s magnetic field acts as a natural particle accelerator. The electrons are forced to spiral rapidly along the magnetic field lines. As they spiral, they release intense, coherent radio waves through a process called the Cyclotron Maser Instability (CMI). You can think of it as a natural radio laser. The frequency of this radio light is directly tied to the strength of the magnetic field at the poles. By measuring the frequency, we can directly calculate the magnetic field strength, a technique that’s impossible with visible light.

Magnetized exoplanets are expected to emit auroral cyclotron radiation in the radio regime.
— Asaf Kaya & Tansu Daylan, Researchers

The beautiful auroras we see on Earth are just the visible part of a much larger phenomenon. Our planet also ‘glows’ in radio waves for the exact same reason: particles from the solar wind interacting with our magnetosphere. This is called Auroral Kilometric Radiation (AKR). The exoplanet signals this study predicts are simply much, much more powerful versions of Earth’s own radio aurora. Hot Jupiters are so close to their stars they are blasted by stellar winds thousands of times more intense than what Earth experiences. This supercharges their magnetospheres, turning them into powerful radio beacons. So, while we can’t see their shimmering light from here, we can potentially *hear* the roar of their gigantic, invisible auroras with our radio telescopes.

The researchers didn’t just plug numbers into a formula. For each of the 1579 planets, many parameters (like stellar age or planetary mass) have uncertainties. To handle this, they used a powerful statistical tool: the Monte Carlo error propagation method. Imagine rolling dice for every uncertain variable, thousands of times for each planet. This process builds a probability distribution, showing not just a single predicted radio strength, but a whole range of likely outcomes. This is Knowledge and Tools in action. It allows them to say with confidence that even with the uncertainties, a planet like tau Boötis b has a high probability of being detectable, making it a prime target for observation campaigns.

Q: If these signals exist, why haven’t we found them yet?
A: Three main reasons: The signals are incredibly faint by the time they reach us, they are beamed like a lighthouse (so Earth has to be in the beam), and our own planet’s ionosphere blocks the lowest-frequency signals from reaching ground-based telescopes.

Q: What is a ‘hot Jupiter’?
A: A hot Jupiter is a gas giant planet similar in size to Jupiter but orbiting extremely close to its parent star, often with an orbital period of just a few days. This proximity makes them incredibly hot and ideal candidates for strong radio emissions.

Q: What happens if they detect a magnetic field on a super-Earth?
A: It would be a monumental discovery. It would provide the first direct evidence that smaller, potentially rocky planets can generate protective magnetic shields, a key ingredient for a planet to be considered potentially habitable.

By the end of this article, you will understand how invisible plasma waves, millions of miles out in space, can trigger tangible, small-scale turbulence in Earth’s upper atmosphere just seconds later, providing a new way to diagnose space weather.

For years, scientists hypothesized a direct link between the magnetosphere and ionospheric turbulence, but catching it in the act was nearly impossible. The Story began by searching for a perfect alignment, or ‘conjunction,’ between the Arase satellite, orbiting near the magnetic equator, and the ICEBEAR radar in Canada. On May 12, 2021, they hit the jackpot. Arase detected a surge in Electrostatic Cyclotron Harmonic (ECH) waves. At almost the exact same time, ICEBEAR, looking at the magnetic ‘footprint’ of Arase’s location, saw a sudden explosion of meter-scale plasma turbulence. The correlation was stunningly precise: the turbulence appeared just 7 seconds after the waves were detected millions of miles away. It was the first direct, unambiguous proof of this rapid connection.

Original Paper: ‘Characteristic E-region Plasma Signature of Magnetospheric Wave-Particle Interactions’

The turbulent transformation of this driving signal can inform development of models that aim to predict the occurrence of plasma turbulence around aurorae.
— Magnus F. Ivarsen et al.

This is NOT a slow, gradual heating process like the sun warming the air. To understand the discovery, we need to build a fence around the concept. Think of the ECH waves in the magnetosphere as a powerful radio transmitter. These waves ‘kick’ electrons out of their normal paths, causing them to rain down into the atmosphere along magnetic field lines. When these high-energy electrons hit the ionosphere, they do two things: 1) they create the diffuse aurora by hitting other particles, and 2) they drastically change the local electric fields. This sudden electrical jolt makes the plasma unstable, creating tiny, intense structures called Farley-Buneman instabilities. The ICEBEAR radar detects the radio waves that bounce off this turbulence. The key is that the turbulence is ephemeral—it dies out almost instantly—so the radar signal faithfully mimics the original wave signal from space.

The resulting image is one of a self-similar and turbulent state, simultaneously measured at points in space separated by 5 Earth radii.
— The Research Team

This discovery is deeply connected to the aurora, specifically the gently glowing ‘diffuse aurora’ and the mysterious ‘pulsating aurora.’ The ECH waves are a key mechanism for scattering electrons from the magnetosphere’s ring current. These scattered electrons are the very same particles that precipitate into our atmosphere to create the auroral light. So, the plasma turbulence is happening in the same regions as the aurora, caused by the exact same stream of incoming particles. The turbulence is the invisible, electrical consequence, while the aurora is the visible, light-producing consequence. By measuring the radar echoes from this turbulence, we get a new diagnostic tool to quantify the energy pouring into our atmosphere during space weather events.

This breakthrough wasn’t luck; it was the result of persistence and incredible technology. The researchers had to comb through over three years of data (Jan 2020 – June 2023) to find one perfect event where the Arase satellite and ICEBEAR radar were perfectly aligned. Arase provided the ’cause’ with its Plasma Wave Experiment, measuring the ECH waves with high precision. ICEBEAR provided the ‘effect,’ using a complex system of multiple interferometry links to create high-resolution 3D maps of the turbulence. By cross-correlating these two completely different datasets, they found the 7-second lag, a number that perfectly matches the time-of-flight for the energetic electrons. This combination of Knowledge and Tools allowed them to see a connection that was previously only theoretical.

Q: What is the ionosphere’s E-region?
A: The E-region is a layer of Earth’s upper atmosphere, typically between 90 to 150 km altitude. It’s high enough to be ionized by solar radiation but low enough that particles still collide frequently, making it a very complex and dynamic region for plasma physics.

Q: Why is a 7-second lag so important?
A: The short delay proves a direct, causal link. It rules out slower processes and matches the physical travel time of energetic electrons from the magnetosphere to the ionosphere, confirming that the waves are directly causing the turbulence via particle precipitation.

Q: Can we feel this turbulence on the ground?
A: No, this turbulence occurs over 100 km above our heads in a very thin plasma. However, it can disrupt radio signals, which is why understanding and predicting it is important for communication and navigation technologies like GPS.

By the end of this article, you will understand why the strange subauroral arc named STEVE looks so different from typical auroras. You’ll learn about the invisible electric engine in our upper atmosphere that creates its unique mauve light and the accompanying ‘Picket Fence’.

For years, the mauve ribbon of light called STEVE puzzled scientists. It appeared equatorward of the aurora, had a unique color, and lacked the high-energy electrons that cause the classic Northern Lights. The Story of this paper is how researchers Evgeny Mishin and Anatoly Streltsov proposed a powerful local engine. They theorized that within fast-flowing rivers of plasma (called SAID channels), a process called the Ionospheric Feedback Instability (IFI) could spontaneously generate intense electric fields. Their computer models showed that in the low-density troughs associated with SAIDs, this IFI process goes into overdrive, creating the exact conditions needed to produce super-energized local electrons that would, in turn, create the signature light of both STEVE and its Picket Fence.

Original Paper: ‘On the Kinetic Theory of Subauroral Arcs’

Ionospheric feedback makes strong small-scale field-aligned currents and electric fields in fast subauroral flows with low-density troughs.
— Key Point from the paper

The Ionospheric Feedback Instability (IFI) is like a natural particle accelerator in our sky. It’s a positive feedback loop. First, a strong electric field from the magnetosphere drives a current in the ionosphere. This current changes the local plasma density. The change in density, in turn, amplifies the electric field, which strengthens the current, and so on. To Build a Fence, this is NOT like the normal aurora, where high-energy particles are shot down from the magnetosphere like a firehose. Instead, IFI is a local process where the ionosphere itself becomes unstable and generates the power. Think of it as the difference between getting wet from a distant rain cloud versus a wave you create in a bathtub that grows until it splashes out.

The IFI ‘splits’ the initial strip into a series of small-scale strips determined by the most unstable wavelength.
— Simplified from the paper

While STEVE is not a traditional aurora, it’s a cousin born from the same fundamental forces: electricity and magnetism interacting with our atmosphere. Normal auroras are the result of particles guided by Earth’s magnetic field from the distant magnetotail. STEVE and Picket Fence are showcases of plasma physics happening much closer, in the ionosphere itself. They demonstrate that our upper atmosphere isn’t just a passive screen for light shows; it’s an active, dynamic electrical environment. This research shows how different configurations of electric fields and plasma density can produce a whole different menu of atmospheric light, expanding our understanding of space weather’s beautiful complexity.

The scientists didn’t catch these electric fields with a net; they revealed them with powerful computation. The Knowledge and Tools involved a two-part simulation. First, they used a ‘two-fluid MHD model’ to simulate how the IFI would evolve in a low-density trough, predicting the strength and location of the parallel electric fields. Second, they fed these predicted electric fields into a different model that solves the ‘Boltzmann kinetic equation’. This is a way of calculating exactly how a population of electrons would gain energy from the fields and how much of that energy would go into making nitrogen and oxygen glow. The fact that the output of their model matched the observed features of STEVE and Picket Fence provides strong evidence for their theory.

Solving the kinetic equation with these fields gives suprathermal electrons and excited neutrals explaining the subauroral arcs features.
— Key Point from the paper

Q: So is STEVE an aurora or not?
A: It’s complicated! The paper suggests the ‘Picket Fence’ is a type of rayed subauroral aurora. STEVE itself is considered a distinct optical phenomenon because its light comes from a hot, flowing gas (thermal emission) rather than direct impacts from high-energy particles from space.

Q: Why the weird mauve or purple color?
A: The color comes from the specific energy the local electrons get from the electric fields. This energy is perfect for exciting nitrogen molecules, causing them to emit light across a broad range of reddish-to-blue wavelengths, which our eyes mix into a mauve or purple continuum. It’s too low to create strong blue/violet auroral lines.

Q: What is a ‘low-density trough’?
A: It’s a channel or trench in the ionosphere where the concentration of plasma is much lower than in the surrounding areas. The paper shows these troughs are the perfect breeding ground for the feedback instability that powers STEVE.

By the end of this article, you will understand how a tiny, invisible plasma phenomenon called the Hall effect acts like a powerful engine, creating giant, swirling ‘ion drift belts’ that completely reshape a moon’s magnetic environment and may even explain its auroras.

For years, scientists used standard models (called resistive MHD) to simulate Ganymede’s magnetosphere. These models painted a clean, symmetric picture of Jovian plasma flowing smoothly around the moon. But this picture didn’t quite match the messy data sent back by the Galileo probe. The Story of this paper is what happened when researchers added a more detailed piece of physics: the Hall effect. Suddenly, their simulations transformed. The neat, symmetric flow vanished, replaced by a dynamic system of asymmetric ion jets and swirling currents. This wasn’t just a small correction; it was a fundamental change to the entire magnetosphere’s structure, revealing a hidden engine that was reshaping the moon’s environment.

Original Paper: ‘The role of the Hall effect in the global structure and dynamics of planetary magnetospheres: Ganymede as a case study’

Hall electric fields in ion-scale magnetic reconnection layers have significant global effects not captured in resistive MHD simulations.
— J. C. Dorelli et al.

The Hall effect happens during magnetic reconnection, where magnetic field lines break and reconnect. Think of this reconnection zone as a thin traffic lane. In this lane, the lighter electrons can make sharp turns, but the heavier ions can’t. This separation of paths creates a powerful electric field. This is NOT just a minor electrical buzz. This Hall electric field acts like a particle accelerator, grabbing ions and flinging them out of the reconnection plane at incredible speeds. The Salient Idea is this force creates jets where none existed before. While older models treated plasma as a single fluid, the Hall effect acknowledges this two-particle reality, revealing a force that changes everything.

The same Hall current system produces a new J x B force that accelerates ions to their local Alfvén speed out of the reconnection plane.
— J. C. Dorelli et al.

Where do auroras come from? They are born from electrical currents, called field-aligned currents (FACs), that flow along magnetic field lines and slam into a planet’s atmosphere. The old models for Ganymede predicted these currents would be strongest on the flanks. However, the Hall effect model shows a completely new system of FACs. These currents are strongest at the upstream and downstream edges of the moon’s polar caps. This is a much better match for where the Hubble Space Telescope has actually observed Ganymede’s auroral ovals. The secret engine of the Hall effect, operating far out in space, may be the direct cause of the beautiful light shows in Ganymede’s sky.

Simulating this was a monumental challenge. The Hall effect happens on the ion inertial scale—a tiny region just a few hundred kilometers wide. But the magnetosphere itself is enormous. To solve this, the team used a clever technique called a nested grid. They created a super high-resolution simulation box right around the moon to capture the microscopic Hall physics. This high-res box was then embedded inside larger, lower-resolution grids that modeled the vast scale of the magnetosphere. It required immense computational power and was like using a microscope and a telescope at the exact same time, allowing them to connect the tiny cause to the moon-sized effect.

Q: Does the Hall effect happen in Earth’s magnetosphere too?
A: Yes, absolutely! The same fundamental physics is at play. However, Earth’s magnetosphere is much larger relative to its ion inertial length, making it incredibly difficult to simulate with current technology. Ganymede serves as a perfect, more manageable ‘natural laboratory’ to study these universal processes.

Q: What is an ‘ion drift belt’?
A: It’s a large-scale, circulating current of ions that flows through Ganymede’s magnetosphere. These ‘belts’ are formed by the powerful ion jets created by the Hall effect, acting like a global conveyor belt that transports plasma around the moon in a highly asymmetric pattern.

Q: What is a ‘double magnetopause’?
A: The Hall effect drives a return flow of plasma that creates a thickened boundary layer on one side of Ganymede. This makes it look like there are two distinct boundaries—an outer one with the main Jovian flow, and an inner one with this returning plasma, creating a ‘double magnetopause’ structure.

By the end of this article, you will understand what a Forbush decrease is, how a solar storm can temporarily shield Earth from galactic cosmic rays, and how scientists use a global network of detectors to see this invisible ‘shadow’ as an early warning for intense auroras.

On November 3-4, 2021, a massive cloud of magnetized plasma from the Sun, an interplanetary coronal mass ejection (ICME), was heading for Earth. As it approached, a network of particle detectors called SEVAN, with stations from Armenia to Germany, watched closely. The Story is not what they saw, but what they *stopped* seeing. Suddenly, the constant rain of high-energy galactic cosmic rays hitting their detectors dropped by 5-10%. This sharp dip is a Forbush decrease. It was the ‘shadow’ of the incoming storm, whose powerful magnetic fields were sweeping cosmic rays aside. This invisible signal was the first sign on the ground that a major geomagnetic storm, one that would soon light up the skies with auroras, was about to begin.

Forbush decrease observed by SEVAN particle detector network on November 4, 2021 (Preprint)

All detectors of the SEVAN network registered a Forbush decrease.
— A. Chilingarian et al.

Imagine Earth is constantly being rained on by tiny, super-fast particles from deep space, called Galactic Cosmic Rays (GCRs). Now, imagine the Sun throws a giant magnetic bubble (an ICME) towards us. This bubble is NOT empty; its magnetic field is dense and turbulent. As it travels, it acts like a giant broom, sweeping GCRs out of its path. When this bubble passes Earth, we temporarily enter a region of space with fewer cosmic rays. This is a Forbush decrease. It is not that the storm is ‘blocking’ the rays like a wall, but rather that it has cleared a path in space that Earth is now moving through. This ‘cleared’ area is the shadow we detect.

Forbush decreases are the most frequent and easy-to-detect phenomenon of solar modulation of galactic cosmic rays.
— Research Paper

The Forbush decrease and auroras are two effects of the same cause. The ICME’s magnetic field that sweeps away cosmic rays is the same one that eventually slams into Earth’s magnetosphere. This impact compresses our planet’s magnetic shield, causing a geomagnetic storm. During this storm, particles are funneled down the magnetic field lines into our atmosphere, especially near the poles. They collide with oxygen and nitrogen atoms, making them glow and creating the aurora. So, observing a Forbush decrease is like getting a telegram that the very same disturbance responsible for a beautiful light show is just a few hours away from making its grand entrance.

This discovery wasn’t made by one person in one lab. It required the SEVAN network, a coordinated effort across multiple countries. These detectors are designed to be identical, so their data can be compared directly. They don’t just count ‘particles’; they are designed with layers that allow scientists to distinguish between high-energy muons, lower-energy charged particles, and neutral particles like neutrons. By looking at the decrease in each particle type separately (Salient Idea), researchers can learn more about the energy and structure of the ICME’s magnetic field. It’s a precise, painstaking process of sifting through cosmic data to forecast events here on Earth.

The big advantage of the SEVAN network is that FD is measured in the fluxes of different particles with various energy thresholds.
— Research Paper

Q: What are cosmic rays?
A: Galactic cosmic rays are high-energy particles, mostly protons and atomic nuclei, that originate from outside our solar system, likely from supernova explosions. They constantly bombard the Earth’s atmosphere.

Q: Is a Forbush decrease dangerous?
A: The decrease itself is not dangerous; it’s just a temporary drop in the normal background radiation. However, it’s a strong indicator that a potentially disruptive geomagnetic storm, which can affect satellites and power grids, is imminent.

Q: Why are detectors placed on mountains?
A: Mountain altitudes have less atmosphere above them to absorb or alter the secondary particles created when cosmic rays hit the air. This results in a stronger signal and a clearer detection of events like a Forbush decrease.

By the end of this article, you will understand how a planet can create a radio signal on its host star, and how scientists use this ‘auroral footprint’ to hunt for exoplanets and their crucial magnetic fields.

How do you find a planet that’s too small and quiet to detect directly with a radio telescope? A team at the University of Leicester came up with a clever solution. Their Story is one of inspiration. They looked at our own solar system, specifically at Jupiter and its moon Io. Io’s movement through Jupiter’s magnetic field creates a powerful electrical circuit, leaving a glowing auroral ‘footprint’ in Jupiter’s atmosphere. The researchers theorized that exoplanets orbiting close to M-dwarf stars could do the same thing on a much grander scale. They built a model to calculate the energy transferred from the planet to the star and predicted the strength of the resulting radio signal. Their work identifies 11 specific systems that might be ‘singing’ right now, waiting to be heard.

Original Paper: ‘Exoplanet-Induced Radio Emission from M-Dwarfs’ by Turnpenney et al.

A region of emission analogous to the Io footprint observed in Jupiter’s aurora is produced.
— Sam Turnpenney et al.

Imagine a river: the stellar wind flowing from the star. Now, put a rock in it: the exoplanet. Normally, the wake flows downstream. But if the river flows slower than the speed of ‘sound’ in that medium (the Alfvén speed), something amazing happens: the disturbance can travel upstream. This is a sub-Alfvénic interaction. This is NOT the planet beaming radio signals into space. Instead, the planet’s presence creates a disturbance in the star’s magnetic field, forming two ‘Alfvén wings’ that act like cosmic wires. These wires carry energy back to the star’s surface. When that energy arrives, it accelerates electrons in the star’s atmosphere, which then release that energy as a focused beam of radio waves.

Energy can be transported upstream of the flow along Alfvén wings.
— NorthernLightsIceland.com Team

The phenomenon described in the paper is a direct cousin to the auroras we see on Earth and Jupiter. The ‘Io footprint’ on Jupiter is a persistent auroral spot caused by the magnetic connection to its moon. This research predicts a similar ‘exoplanet footprint’ on M-dwarf stars. For a planet to create this effect, it needs either a protective magnetic field or a thick atmosphere to act as an obstacle. Therefore, detecting this radio signal is a powerful clue that the planet has a magnetic shield. That shield is the single most important factor in protecting an atmosphere from being stripped away by the stellar wind—a prerequisite for life as we know it and for any planet to host its own auroras.

This wasn’t just a guess; it was a feat of calculation. The researchers used a model of stellar wind (the Parker spiral) to determine the plasma conditions around the star. They then calculated the ‘Poynting flux’—the amount of energy carried along the Alfvén wings. Finally, they estimated how much of that energy would be converted into radio waves by the electron-cyclotron maser instability (ECMI). To make their predictions, they had to estimate planetary properties, like magnetic field strength, using scaling laws. They ran these calculations for 85 known exoplanets orbiting M-dwarfs to create a priority list for radio telescopes like the VLA and the future SKA, turning a theoretical idea into a concrete observation plan.

Q: So, are we listening to aliens?
A: No, we are not listening for intelligent communication. We are listening for a natural radio emission caused by the physical interaction between a planet and its star, similar to how Jupiter’s moons create auroras.

Q: Why can’t we just listen to the planet’s own radio signal?
A: For Earth-sized planets, the radio signals they might produce are at very low frequencies. These signals get trapped by the planet’s own ionosphere and can’t escape into space for us to detect. This indirect method bypasses that problem by having the much more powerful star do the broadcasting.

Q: Does this mean these planets have life?
A: Not directly, but it’s a huge step. A strong magnetic field is essential for protecting a planet’s atmosphere, which is a key requirement for habitability. Finding a magnetic field would be a very promising sign.

By the end of this article, you will understand the invisible magnetic web that connects stars and planets, a force so powerful it can create cosmic shocks, cause stellar storms, and even drag entire planets out of their orbits.

When astronomers began discovering thousands of ‘hot Jupiters’—gas giants orbiting incredibly close to their stars—they found phenomena that gravity alone couldn’t explain. The Story began with puzzling observations: some host stars showed strange, synchronized flare-ups, while others seemed to have ‘cleared out’ zones with no close-in planets. Scientists realized these planets were so close they were orbiting *inside* the star’s extended magnetic field. This triggered a wave of research into star-planet magnetic interaction (SPMI). The models reviewed in this paper show how this interaction can explain the mysteries: planets ‘poking’ their stars to cause flares, and a magnetic ‘drag’ so powerful it could make planets spiral to their doom, explaining the empty zones.

Original Research Paper: ‘Models of Star-Planet Magnetic Interaction’

Magnetic interactions are today a serious candidate to explain these fascinating phenomena.
— Antoine Strugarek, Astrophysicist

Imagine a planet so close to its star that the star’s magnetic field is stronger than the stellar wind pushing outwards. This is the sub-Alfvénic regime. Now, this isn’t just a static field; it’s a dynamic plasma environment. As the planet orbits, it plows through this magnetic medium, creating a disturbance. The key concept is the Alfvén Wing. Instead of the disturbance spreading out, the energy gets focused and channeled along the magnetic field lines, creating two ‘wings’ that connect back to the star. This is NOT like a simple magnetic attraction. It’s an active, energetic connection that transfers momentum and power, acting like both a brake and a generator. It’s a constant, powerful interaction driven by the planet’s motion.

A close-in planet can be viewed as a perturber orbiting in the likely non-axisymmetric inter-planetary medium.
— Antoine Strugarek, Astrophysicist

The beautiful auroras on Earth happen when the solar wind interacts with our planet’s magnetic field, channeling energy and particles into our atmosphere. Star-planet magnetic interaction is this exact process, scaled up to an incredible degree. The Alfvén wings are like the magnetic field lines that guide particles to Earth’s poles, but they carry vastly more energy. When this energy slams back into the star’s atmosphere, it can create a starspot—a stellar aurora. When it hits the planet’s atmosphere, it can trigger planetary auroras that would be thousands of times more powerful than our own. Studying these extreme interactions helps us understand the fundamental physics that protects Earth’s atmosphere and gives us our own gentle light shows.

Modeling these interactions is incredibly hard. Early researchers used clever analogies, like treating the star-planet system as a simple electric circuit (the ‘unipolar inductor’ model). The planet’s motion acted as a generator, the magnetic field lines were the wires, and the planet and star were resistances. While useful, this was too simple. The real progress came from 3D magnetohydrodynamic (MHD) simulations. These are complex computer models that treat the star’s wind as a magnetized fluid. Researchers spend immense effort creating realistic ‘boundary conditions’ for the planet and star to ensure the simulation is accurate. These models, like those shown in the paper, are the tools that allow us to visualize the invisible magnetic games playing out between stars and their planets.

Q: Can this magnetic interaction happen between the Sun and Earth?
A: Yes, but it’s much, much weaker. Earth is far outside the Sun’s sub-Alfvénic zone, where the solar wind dominates. The interactions described in the paper are for exoplanets orbiting hundreds of times closer to their star than Earth does to the Sun.

Q: Can we actually see these magnetic fields?
A: Not directly, but we can see their effects. We can look for synchronized stellar flares, absorption of starlight from a planet’s bow shock just before it transits, or radio emissions from the planetary aurorae. These are the observable clues that tell us the magnetic interactions are happening.

Q: Could this force eventually destroy a planet?
A: Absolutely. The magnetic torque can cause a planet’s orbit to decay, making it spiral closer and closer to its host star until it’s consumed. This is a leading theory for why we don’t find many planets in extremely close orbits around certain types of stars.

By the end of this article, you will understand why your compass doesn’t point to the geographic North Pole and how scientists use special ‘magnetic maps’ to track space weather and predict where the aurora will appear.

For centuries, we’ve known Earth acts like a giant bar magnet. Scientists first built coordinate systems based on this simple idea, called Centered Dipole (CD) coordinates. It was a good start, but observations of space phenomena didn’t quite line up. So, they created a more refined model where the ‘bar magnet’ was shifted from the Earth’s center—the Eccentric Dipole (ED) model. But even that wasn’t enough. The real magnetic field is complex and lumpy. The breakthrough came when scientists abandoned simple magnets and started using computers to trace the actual magnetic field lines from the full International Geomagnetic Reference Field (IGRF). This created incredibly accurate but mathematically tricky systems like Corrected Geomagnetic (CGM) and Quasi-Dipole (QD) coordinates, which are now essential for modern space science.

Original Paper: ‘Magnetic Coordinate Systems’ in Space Science Reviews

The improved accuracy comes at the expense of simplicity, as the result is a non-orthogonal coordinate system.
— K.M. Laundal & A.D. Richmond

Imagine a regular map grid where every line of latitude and longitude crosses at a perfect 90-degree angle. That’s an orthogonal system. Now, imagine stretching and warping that grid in some places. The lines would no longer be perpendicular. That’s a non-orthogonal system, and it’s exactly what the most accurate magnetic coordinates are like. This is NOT a mistake; it’s a true representation of Earth’s complex field. The key idea is that these coordinates are constant along a given magnetic field line. So if you travel up or down a field line, your Quasi-Dipole latitude and longitude don’t change. This makes them incredibly powerful for studying things like the aurora, which are guided by these very lines.

The deviation from orthogonality is particularly significant in the South Atlantic and in the southern parts of Africa.
— K.M. Laundal & A.D. Richmond

The aurora is like a giant neon sign in the sky, lit up by charged particles from the solar wind that are guided by Earth’s magnetic field. If you plot auroral sightings on a regular geographic map, they appear in a scattered, messy pattern. But if you use a magnetic coordinate system like Corrected Geomagnetic (CGM) coordinates, the pattern snaps into focus: a perfect ring around the magnetic pole, known as the auroral oval. This is because the particles follow the magnetic field lines, not lines of geographic longitude. These coordinate systems are the ‘Rosetta Stone’ that allows us to understand the shape, location, and dynamics of the aurora, connecting what we see in the sky to the vast magnetic structures that protect our planet.

Scientists can’t just ‘look’ at a magnetic field line. The work involves complex computation. They start with the International Geomagnetic Reference Field (IGRF), a global model built from satellite and ground-based magnetometer data. Using this model, they perform a process called field line tracing. A computer program starts at a specific point in the ionosphere (e.g., 110 km altitude) and calculates the direction of the magnetic field vector. It then takes a small step in that direction, recalculates, and repeats, stepping along the invisible magnetic line through space. By tracing this line to its highest point (the apex) or to where it crosses the equator, they can define accurate magnetic coordinates. This hard computational work is what makes modern, precise space weather forecasting possible.

Q: Why are there so many different magnetic coordinate systems?
A: Different systems are tools for different jobs and different regions of space. Simple ‘dipole’ systems are good for high altitudes where the field is simple, while complex ‘field-line traced’ systems are needed for accuracy in the ionosphere where the aurora happens.

Q: What’s the difference between the magnetic pole and the geomagnetic pole?
A: The ‘magnetic pole’ (or dip pole) is where the field lines point straight down, which is what a compass would lead you to. The ‘geomagnetic pole’ is a theoretical concept based on the best simple dipole approximation of Earth’s field. They are in different locations and both move over time.

Q: Do I need to worry about this for my compass?
A: For basic navigation, your compass works fine by pointing to the magnetic dip pole. These advanced coordinate systems are specialized tools for scientists studying plasma physics and space weather on a global scale.

By the end of this article, you will understand why auroras don’t just hang there as curtains, but can form stunning street-like patterns of whirlpools, and how this is driven by a complex electrical circuit connecting Earth to deep space.

Scientists have long observed that at the start of a powerful auroral display (a substorm), simple arcs of light can suddenly brighten, split, and twist into a row of swirling vortices. But what causes this rapid, beautiful chaos? To solve this, Dr. Yasutaka Hiraki didn’t use a telescope. He used a supercomputer. The Story of this discovery is one of digital recreation. He created a 3D simulation of the ionosphere, placed a simple auroral arc inside it, and then simulated a surge of energy from space—an enhanced electric field. The result was stunning: the simulated arc buckled and deformed into a perfect vortex street in just 30-40 seconds, matching real-world observations. By analyzing the flow of currents in his simulation, he pinpointed the exact electrical feedback loop responsible for the dance.

Ionospheric current system accompanied by auroral vortex streets – Hiraki, Y. (2016)

Our previous work reported that an initially placed arc intensifies, splits, and deforms into a vortex street during a couple of minutes, and the prime key is an enhancement of the convection electric field.
— Yasutaka Hiraki, Author

This swirling isn’t just a random pattern. It’s caused by a specific process called Cowling Polarization. To understand it, let’s build a fence around the concept: this is NOT like water swirling down a drain. It’s an electrical feedback loop. Imagine two types of currents flowing horizontally in the ionosphere: the Hall current and the Pedersen current. When a bright aurora forms, it acts like a roadblock for the main Hall current. This causes electrical charge to pile up on the edges of the aurora. This pile-up creates a *new* electric field. This new field then drives a Pedersen current, which flows in a different direction and helps complete the circuit. The interaction between the original current, the roadblock, and the new current is what kicks off the spinning motion that forms the vortex.

One component is due to the perturbed electric field by Alfvén waves, and the other is due to the perturbed electron density (or polarization) in the ionosphere.
— Yasutaka Hiraki, Author

These vortex streets, while appearing as local phenomena, are deeply connected to the grand-scale behavior of Earth’s magnetic field. They are the ionospheric footprints of Alfvén waves—powerful magnetic waves that travel from the Earth’s distant magnetotail, a region where immense energy from the solar wind is stored. When this stored energy is suddenly released during a substorm, it sends these waves racing towards Earth. The waves deliver the extra energy and electric field that destabilize the calm auroral arcs. So, when you see a vortex, you’re witnessing the precise moment that energy from millions of miles away makes its dramatic entrance into our atmosphere, all guided by the invisible architecture of our planet’s magnetic shield.

This research is a perfect example of how modern science uses Knowledge and Tools. The core of this work is a ‘three-dimensional magnetohydrodynamic (MHD) simulation’. This is a fancy way of saying they created a virtual box of plasma (the superheated gas that makes up the aurora) and programmed in the fundamental laws of physics that govern how electricity, magnetism, and fluids interact. They then set the initial conditions—a calm atmosphere with a simple auroral arc—and pressed ‘play’. By observing how this digital aurora evolved when ‘poked’ by an external electric field, they could dissect the complex, high-speed chain of events in a way that is impossible to do by just looking at the sky.

Q: Why do the vortices form in a ‘street’ or a row?
A: This pattern, known as a von Kármán vortex street, is common in fluid dynamics when a flow is disturbed. The instability in the auroral arc naturally settles into this organized, repeating pattern of counter-rotating swirls, which is the most energy-stable configuration.

Q: Can we see these auroral whirlpools with the naked eye?
A: Yes, but it requires a very active and fast-moving aurora. They happen quickly, so they are often better captured by sensitive, high-speed cameras that can reveal the swirling structure that might look like a chaotic flicker to our eyes.

Q: What’s the difference between Pedersen and Hall currents?
A: In the ionosphere, an electric field pushes charged particles. The Pedersen current flows in the direction of this electric field. However, because of Earth’s magnetic field, electrons are deflected sideways, creating the Hall current, which flows perpendicular to both the electric and magnetic fields.

By the end of this article, you will understand the hidden feedback loop that makes auroras suddenly explode in brightness, and why a ‘rain’ of electrons is the key to flipping the switch.

For years, scientists were puzzled. Their models showed that for a quiet auroral arc to erupt into a dazzling display, it needed a very strong ‘push’ from a background electric field—about 25 to 45 millivolts per meter (mV/m). Yet, real-world radar observations showed these intensifications happening at much lower levels, around 10-20 mV/m. There was a disconnect between theory and reality. Dr. Yasutaka Hiraki’s research presents the Story of the solution. He introduced a crucial, previously under-appreciated effect: the ionization caused by precipitating electrons. These falling electrons energize the atmosphere, making it a better conductor. This single change in the model dramatically lowered the required energy threshold, perfectly aligning the theory with real-world observations.

Original Research: ‘Threshold of auroral intensification reduced by electron precipitation effect’ by Y. Hiraki

It was found that the threshold of convection electric fields is significantly reduced by increasing the ionization rate.
— Yasutaka Hiraki, Researcher

Imagine Earth’s connection to space as a giant electrical circuit. The magnetosphere is the power source, and the ionosphere (our upper atmosphere) is like a resistor. Energy travels down this circuit via Alfvén waves. Now, this is NOT just about the waves delivering power. The key idea is that as these waves hit the atmosphere, they cause electrons to ‘precipitate’ or rain down. This rain of electrons ionizes the neutral air, which dramatically *lowers* the atmosphere’s electrical resistance. With lower resistance, the same amount of power from the magnetosphere can drive a much stronger current and amplify the Alfvén waves even more. This creates a runaway feedback loop, causing the aurora to suddenly and intensely brighten. It’s a self-fueling process.

This research directly explains one of the most beautiful sights in the Arctic: the explosive onset of an auroral substorm. You might see a faint, quiet green arc hanging in the sky for minutes. Then, seemingly without warning, it erupts into swirling, dancing curtains of light that fill the sky. That sudden change is the moment the system crosses the now-lowered threshold. The positive feedback loop kicks in, the Alfvén wave instability grows exponentially, and the energy flowing down Earth’s magnetic field lines intensifies dramatically. The electron ‘rain’ didn’t just add to the light; it changed the rules of the game, allowing the main event to begin with less of a push.

The prime key is an enhancement of plasma convection, and the convection electric field has a threshold.
— Yasutaka Hiraki, Researcher

This breakthrough didn’t come from a new telescope, but from powerful computer modeling and theoretical physics. Dr. Hiraki used a set of complex mathematical equations to simulate the magnetosphere-ionosphere (M-I) coupling system. This ‘digital twin’ of the auroral circuit allowed him to change one variable at a time. He modeled how Alfvén waves propagate and interact with the ionosphere. The crucial step was adding a term to his equations representing the ionization from precipitating electrons (the ‘q’ value). By running simulations with different ‘q’ values, he demonstrated precisely how this effect lowered the instability threshold, providing a clear, mathematical explanation for a long-standing mystery in space physics.

Q: What are Alfvén waves?
A: Alfvén waves are a type of electromagnetic wave that travels along magnetic field lines in a plasma. You can think of them like a vibration traveling down a guitar string, except the ‘string’ is one of Earth’s magnetic field lines, and the ‘vibration’ is carrying electrical current and energy that powers the aurora.

Q: So the falling electrons ARE the aurora?
A: Yes and no. The light of the aurora is produced when falling electrons strike atmospheric gases. But this research shows their *other* job is just as important: they change the conductivity of the atmosphere, which allows the *entire system* that accelerates them to become more powerful and unstable.

Q: Why is a ‘threshold’ so important?
A: A threshold explains why auroral displays aren’t constant. They can remain calm for a long time and then suddenly erupt. The system has to build up enough energy to cross that tipping point, and this research shows that electron precipitation effectively lowers the bar, making those eruptions happen more easily.

By the end of this article, you will understand how scientists use the Hubble Space Telescope to read the ‘light shows’ on giant planets, and how these auroras act as a powerful diagnostic tool for invisible magnetic fields and dangerous space weather.

For years, scientists have paired the Hubble Space Telescope with deep space probes for a one-two punch of discovery. The Story is one of perfect synergy: a probe like Cassini orbiting Saturn gets ‘in the mud’, measuring particles and magnetic fields up close, but it’s too close to see the whole picture. At the same time, Hubble, from its distant perch, captures the entire auroral oval in a single snapshot. By combining these two views, scientists can directly link a specific storm in the solar wind or a change in the magnetotail to a visible flare-up in the aurora. This paper highlights a unique opportunity in 2016-2017 when the Cassini mission at Saturn and the new Juno mission at Jupiter were both in their prime, creating a ‘Grand Finale’ of comparative studies.

Read the Original ‘White paper submitted in response to the HST 2020 vision call’

Such synergistic observations proved to be essential to assess complex magnetospheric processes.
— L. Lamy et al.

An aurora is NOT like a neon sign that is simply switched on. It is a dynamic process. It begins when charged particles—from the solar wind or a volcanic moon like Io—get trapped in a planet’s magnetic field. This field, like an invisible funnel, channels these high-energy particles toward the poles. As they accelerate down the magnetic field lines, they violently collide with gas in the upper atmosphere (like hydrogen on Jupiter). This collision excites the gas, causing it to glow. So, the aurora is a direct visual trace of where energy is being dumped into a planet’s atmosphere. Let’s build a fence: this is fundamentally different from a planet just reflecting sunlight. This is light the planet is *creating* itself in response to its space environment.

Auroras are the best window we have into a planet’s magnetosphere—its protective magnetic shield. On Earth, this shield deflects the harmful solar wind, protecting our atmosphere and enabling life. Giant planets have magnetospheres thousands of times stronger. The size, shape, and brightness of their auroras tell us exactly how that shield is interacting with the solar wind, its own moons, and its rapid rotation. The Salient Idea is that by studying the ‘weird’ auroras of a planet like Uranus, with its tumbling magnetic field, we learn about the fundamental physics that governs all magnetic fields, including the one that keeps us safe here on Earth. They are cosmic laboratories for space weather.

Aurorae are therefore a direct, powerful, diagnosis of the electrodynamic interaction between planetary atmospheres, magnetospheres, moons and the solar wind.
— L. Lamy et al.

Getting these images isn’t easy; it’s a testament to Knowledge and Tools. Scientists use specialized instruments on Hubble like STIS (Space Telescope Imaging Spectrograph) that can see in Far-Ultraviolet (FUV) light, which is invisible to our eyes but where hydrogen auroras shine brightest. The real challenge comes with the ice giants. The paper describes the difficult hunt for Uranus’s aurora. After failed attempts, they realized the emissions were too faint to see under normal conditions. Their solution was clever: they used models to predict when a solar storm (an interplanetary shock) would hit Uranus, and scheduled Hubble’s precious time to observe right then, maximizing their chances of seeing the aurora flare up. This shows research is not just pointing and shooting; it’s a game of strategy and prediction.

Q: Why can’t probes like Juno just take pictures of the whole aurora?
A: A probe like Juno flies very close to the planet. It’s like trying to take a picture of an entire football stadium while standing on the field. You get incredible detail of the grass and players near you, but you can’t see the whole game at once. Hubble provides that wide, contextual view from the nosebleed seats.

Q: Are auroras on other planets different colors?
A: Absolutely! The color of an aurora depends on what gas is being excited in the atmosphere. Earth’s are famously green and red from oxygen and nitrogen. Jupiter and Saturn’s atmospheres are mostly hydrogen, so their main auroras glow in pink and ultraviolet, which our eyes can’t see without special instruments.

Q: Do planets without magnetic fields have auroras?
A: Generally, no. A strong, global magnetic field is the key ingredient for creating the distinct auroral ovals at the poles. Planets like Venus and Mars lack this shield, so while they have some high-altitude ‘airglow’, they do not have the structured, powerful auroras we see on Earth or the giant planets.

By the end of this article, you will understand how the direction of the interplanetary magnetic field (IMF) acts like a key, either locking Earth’s magnetic shield tight or opening cosmic highways for solar particles to create auroras.

In 1907, Carl Störmer created a mathematical map for charged particles moving around Earth. His theory showed there were ‘allowed’ and ‘forbidden’ zones, explaining why some cosmic rays could reach us and others were deflected. But his model treated Earth’s magnetic field in isolation. The Story of this research is how J.F. Lemaire updated that map by adding one crucial detail: the Interplanetary Magnetic Field (IMF) carried by the solar wind. Lemaire showed that when the IMF points southward, it fundamentally changes the rules. It lowers the energy barriers and creates ‘interconnected’ pathways, allowing solar particles to flow into regions that were previously forbidden. This solved the long-standing problem of how auroral electrons could so effectively penetrate our defenses.

Lemaire, J.F., ‘The effect of a southward interplanetary magnetic field on Störmer’s allowed regions’

A southward turning of the IMF orientation makes it easier for Solar Energetic Particle and Galactic Cosmic Rays to enter into the inner part of the geomagnetic field.
— J.F. Lemaire, The Author

Imagine the space around Earth as a mountainous landscape of magnetic potential. In Störmer’s original theory, trapped particles, like those in the Van Allen belts, are stuck in a deep, closed-off valley called the ‘Thalweg’. To get in or out, a particle needs enough energy to climb over the high mountain pass. Now, let’s build a fence around this concept. This isn’t just about magnetic field lines guiding particles. It’s about an energy barrier. The Salient Idea is that a southward IMF doesn’t just nudge the particles; it lowers the entire mountain pass. Suddenly, particles with much lower energy can stream into the valley from interplanetary space, or escape from it. A northward IMF does the opposite: it raises the pass, locking the door even tighter.

The ‘pass’ between the inner and outer allowed zones opens up, when -F increases.
— J.F. Lemaire, The Author

The aurora is the result of energetic particles from the sun hitting our upper atmosphere. But how do they get there? Lemaire’s work provides the answer. A southward IMF creates what he calls ‘interconnected magnetic field lines.’ Think of these as direct highways leading from the solar wind, over the lowered ‘mountain pass,’ and down into the polar regions (the cusps). Particles can then spiral freely down these highways without needing to overcome a huge energy barrier. This is why aurora forecasts are so dependent on the ‘Bz’ component of the IMF. A negative Bz (southward) means the cosmic highways are open for business, leading to a much higher chance of vibrant auroras.

Instead of relying on massive, computer-intensive simulations that trace billions of individual particles, this study used a powerful analytical approach. Lemaire extended Störmer’s original mathematical framework, which assumed perfect cylindrical symmetry. By adding a uniform north-south magnetic field, he could derive a new, simple equation for the ‘Störmer potential.’ This elegant mathematical work allowed him to see the big picture: how the entire topology of allowed and forbidden zones shifts. It’s a prime example of how a deep understanding of the underlying physics and clever mathematics can reveal fundamental truths that might be missed in the complexity of a full simulation.

Q: What happens when the IMF is pointing northward?
A: When the IMF is northward, the magnetic ‘mountain pass’ gets higher. This makes it much harder for solar particles to enter the inner magnetosphere and makes it more difficult for particles already trapped in the radiation belts to escape.

Q: Is Störmer’s original theory wrong then?
A: No, it’s not wrong, just incomplete for describing real-world space weather. It’s a foundational model that works perfectly for a pure dipole magnetic field. Lemaire’s work is an extension that adds another layer of reality—the external IMF—to make it more accurate.

Q: Does this apply to other planets?
A: Absolutely! Any planet with a significant magnetic field, like Jupiter or Saturn, will experience similar effects. The interaction between their magnetospheres and the solar wind’s IMF will determine how particles get in and create their own massive auroras.

By the end of this article, you will understand how scientists discovered the first direct evidence of ‘cavitating turbulence’—a process where intense plasma waves create dynamic, energy-filled bubbles inside the aurora.

On a November night in 1999, scientists at the EISCAT radar in Norway were studying an intense aurora. They weren’t just watching the lights; they were probing the plasma high above. Their experiment was designed to detect two types of plasma waves: Langmuir and ion-acoustic. Suddenly, their screens lit up with a pattern that had been theorized but never seen in the wild. They detected strong signals from *both* types of waves at the same altitude and time. Even more telling was a Surprise feature in the ion-acoustic data: a strong, stationary central peak. This specific combination was the predicted ‘fingerprint’ of cavitating Langmuir turbulence. The data showed that the aurora’s electron beam was powerful enough to not just create waves, but to make those waves violently carve out bubbles in the plasma itself.

Original Paper: ‘Cavitating Langmuir Turbulence in the Terrestrial Aurora’

The data presented here are the first direct evidence of cavitating Langmuir turbulence occurring naturally in any space or astrophysical plasma.
— B. Isham et al.

This process is called ‘cavitating Langmuir turbulence.’ Imagine a powerful beam of auroral electrons shooting through the ionosphere’s plasma. This creates high-frequency energy waves, called Langmuir waves. Now, this is NOT like ripples in a pond. When these waves become incredibly intense, they act like a snowplow, physically pushing the surrounding charged particles out of the way. This creates a temporary, low-density ‘bubble’ or cavity—a caviton. The Langmuir waves then become trapped inside their own bubble, which makes them even stronger, until the whole structure collapses. This is the difference between gentle ‘weak’ turbulence and this violent, self-reinforcing ‘strong’ turbulence.

In its most developed form, this turbulence contains electron Langmuir modes trapped in dynamic density depressions known as cavitons.
— Research Paper Abstract

The Northern Lights are more than just a beautiful display; they are the visible result of Earth’s magnetic field guiding high-energy electrons from the solar wind into our upper atmosphere. These same beams of electrons act as the engine for cavitating turbulence. The aurora provides the ‘pump’ of energy needed to drive plasma waves to their breaking point, where they begin to form cavitons. This discovery shows that the beautiful, dancing curtains of light are also sites of incredibly energetic and complex plasma physics. Understanding this process helps us model space weather and how energy from the sun is deposited into our atmosphere, which can affect satellites and radio communication.

This discovery relied on the perfect combination of Tools and Knowledge. The tool was the EISCAT incoherent scatter radar, which can measure the faint echoes from different plasma waves. The knowledge came from the Zakharov equations, a set of theoretical physics equations from the 1970s that describe this exact behavior. The researchers ran computer simulations using these equations, feeding them the plasma conditions measured during the aurora (see Figure 4). The simulated radar signal was a near-perfect match for what they observed in reality (Figure 3), specifically the enhanced ‘shoulders’ and the critical ‘central peak’. This match between observation and simulation turned a strange radar signal into a landmark discovery.

Q: What is ‘Langmuir turbulence’?
A: It’s a type of disturbance that happens in plasma, which is a gas of charged particles. When a beam of electrons passes through it, it can create waves, much like a speedboat creates a wake in water. This paper is about a particularly strong, or ‘cavitating,’ form of this turbulence.

Q: Why is this discovery so important?
A: Scientists had created this effect in labs and predicted it happened in space, but this was the first time they found direct proof of it occurring naturally. It confirms a fundamental theory of plasma physics and shows it happens in places like the aurora, pulsars, and the sun’s corona.

Q: Can we see these ‘cavitons’ with our eyes?
A: No, they are far too small, only a few meters across, and occur in the very thin plasma of the ionosphere hundreds of kilometers up. We can only detect their effects using highly sensitive instruments like the EISCAT radar.

By the end of this article, you will understand a powerful and simple new way to think about space weather: that Earth’s magnetosphere physically expands and contracts like it’s breathing, and how this simple idea explains the complex relationship between magnetic storms, substorms, and the aurora.

For decades, scientists have used a complex model called ‘magnetic reconnection’ to explain space weather. But some observations never quite fit, like why the main phase of a magnetic storm begins *before* the first substorm, or why substorms can sometimes weaken a storm. This research proposes a simpler Story: what if the magnetosphere behaves like a simple physical object? The paper shows that by treating the interaction as an attraction or repulsion—like two magnets—many of these puzzles disappear. A southward Interplanetary Magnetic Field (IMF) attracts and expands Earth’s field, creating a storm. A northward IMF repels and contracts it. This ‘breathing’ model provides an intuitive framework that matches observations without the theoretical problems of older models.

Original Paper: ‘Magnetic Storm-substorm Relationship and Some Associated Issues’ by E. P. Savov

The expansion (contraction) of magnetosphere accounts for the observed expansion (contraction) of the auroral oval.
— E. P. Savov, Researcher

Imagine the Sun sends out a magnetic field (the IMF). When the IMF arriving at Earth points south, its field lines align with Earth’s in an attractive way. This pulls Earth’s magnetic shield outward, expanding it and allowing it to capture more energy and particles from the solar wind. This is the ‘growth phase’ of a storm. Now, let’s build a fence: this is NOT the same as ‘magnetic reconnection’ where field lines are thought to break and re-form. Think of it more as a balloon inflating. Conversely, when the IMF points north, the fields repel each other. This squeezes and contracts the magnetosphere, pushing the solar wind away more effectively and leading to calmer space weather. The Salient Idea is that this simple push-and-pull dynamic governs the entire system.

The location of the aurora is a direct visual indicator of this breathing. During a magnetic expansion (southward IMF), the boundaries of the magnetosphere are pushed out, and the auroral oval shifts towards the equator. This is why auroras are seen at lower latitudes during big storms. During a contraction (northward IMF), the oval shrinks back towards the pole. What about a substorm? The model explains the explosive phase as a rapid, partial *contraction* of the over-stretched magnetotail. This contraction violently flings particles back towards Earth, creating the bright, dynamic auroral surges on the poleward edge of the oval. A very strong, prolonged contraction can even bifurcate the magnetotail, creating the rare and beautiful transpolar arc known as a ‘theta aurora’.

This isn’t just an idea; it’s backed by calculation and a proposal for a physical test. The author calculated the expected average thickness of the magnetopause boundary layer based on the observed 45-minute expansion and 8-hour contraction times of the aurora. The result, about 0.44 Earth radii, matches spacecraft observations perfectly. To further prove the concept, the paper outlines an upgrade to the famous 19th-century ‘terrella’ experiment. By adding a second large magnetic coil to simulate the IMF, a lab could physically demonstrate the expansion and contraction of the artificial auroral oval by simply flipping the polarity of the external ‘solar’ magnet. This brings a grand cosmic theory down to a testable, hands-on experiment.

The suggested 3D-spiral magnetic reconfiguration… avoids the topological crisis.
— E. P. Savov, on why this model is simpler

Q: So does a substorm cause a magnetic storm?
A: According to this model, no. A magnetic storm is a large expansion of the magnetosphere caused by a long period of southward IMF. A substorm is a smaller expansion (growth phase) followed by a rapid, partial contraction (expansion phase) that releases energy, often weakening the larger storm.

Q: Why is this model better than the old ‘magnetic reconnection’ one?
A: The author argues it’s simpler and avoids certain theoretical problems, a principle known as Occam’s Razor. It explains confusing observations, like the storm-substorm timing, more intuitively by likening the magnetosphere’s behavior to simple magnetic attraction and repulsion.

Q: What happens when the solar wind pressure increases?
A: Higher solar wind pressure pushes on the magnetosphere, creating a longer, thicker magnetotail. This thicker tail is better at ‘catching’ the southward IMF, which then drives an even stronger expansion and a more intense magnetic storm.

By the end of this article, you will understand how astronomers create weather maps for worlds light-years away and learn that the ‘weather’ on some objects is driven by powerful auroras, not clouds.

A team of astronomers used the JWST to stare at SIMP-0136, a nearby brown dwarf, for one full rotation. They expected a familiar Story: that the object’s flickering brightness was caused by patchy clouds rotating in and out of view. But their computer models, designed to work backward from the light spectra, revealed a Surprise. To explain the data, the clouds had to be mostly static. The real action was a dramatic temperature change high in the stratosphere. At all times, there was a ‘thermal inversion’—a layer about 250 Kelvin hotter than it should be. The primary variability wasn’t from clouds below, but from this mysterious heat from above.

Original Research Paper: ‘The JWST weather report: Retrieving temperature variations, auroral heating, and static cloud coverage on SIMP-0136’

This work paints a portrait of an L-T transition object, where the primary variability mechanisms are magnetic and thermodynamic in nature, rather than due to inhomogeneous cloud coverage.
— E. Nasedkin et al., Lead Authors

Normally, as you go higher in a planet’s troposphere, it gets colder. A thermal inversion flips this script: a layer of the atmosphere is hotter than the layer below it. This is NOT like the ground warming up on a sunny day. An inversion requires energy to be deposited directly into the upper atmosphere, like a heater installed in the ceiling. On Earth, our ozone layer does this with UV light. On SIMP-0136, with no star nearby, the energy source must be different. The Salient Idea is that this inversion acts as a giant fingerprint pointing to an external energy source—in this case, energetic particles guided by a magnetic field.

The temperature gradient inverts, and begins increasing with increasing altitude… This is clearly in contrast with the self-consistent forward models, which are usually monotonically decreasing.
— From the Research Paper

The heat source is almost certainly a powerful aurora. Previous radio observations already hinted that SIMP-0136 has one. The research suggests a magnetic field of around 3000 Gauss—hundreds of times stronger than Jupiter’s—is accelerating particles and slamming them into the atmosphere. This is the same process that creates Earth’s Northern Lights, but on an epic scale. These particles dump their energy high in the stratosphere, creating the observed permanent ‘heat wave’. SIMP-0136 is a self-contained aurora generator, teaching us how magnetic fields can fundamentally shape planetary atmospheres, even in the lonely darkness between stars.

This discovery relied on a technique called time-resolved atmospheric retrieval. The team didn’t just take one snapshot; they collected thousands of light spectra over 3.5 hours as the brown dwarf rotated. Each spectrum was fed into a complex computer model called `petitRADTRANS`. This program tested millions of possible atmospheric conditions—different temperatures, chemicals, and cloud structures—to find the combination that perfectly matched the JWST data for that specific moment. By comparing the ‘best-fit’ models from 24 different rotational phases, they built a dynamic weather map and proved the temperature, not the clouds, was the main thing changing.

Q: If the clouds aren’t changing, why does SIMP-0136 have them?
A: The models show that patchy silicate clouds are necessary to explain the overall spectrum of SIMP-0136. However, these patches don’t seem to rotate in a way that causes the main brightness variations. They are a static feature of the landscape, while the temperature changes are the active ‘weather’.

Q: Can we see this aurora with our eyes?
A: Probably not. The auroral emission signatures typically sought, like H3+, haven’t been detected yet. The ‘aurora’ here is detected indirectly through the intense heating it causes in the atmosphere, which JWST can measure in the infrared.

Q: How can it have an aurora without a sun and solar wind?
A: The mechanism isn’t fully understood, but it’s believed that rapidly rotating brown dwarfs like SIMP-0136 can generate their own charged particles and powerful magnetic fields. This creates a self-contained system that powers its own aurora, independent of a nearby star.

By the end of this article, you will understand how astronomers use the JWST to create a ‘weather report’ for a planet without a star, revealing a complex atmosphere where clouds, auroral hot spots, and chemical changes all happen simultaneously at different altitudes.

Scientists pointed the James Webb Space Telescope at SIMP 0136+0933, a well-known rogue planet, to watch its weather over one full 2.4-hour rotation. The Story they uncovered was far more complex than just the patchy clouds seen before. As the planet spun, its brightness changed, but the pattern of that change was different depending on the wavelength of infrared light they looked at. Some patterns had one dip in brightness, others had two. To solve this puzzle, they realized they weren’t seeing one weather system, but several stacked on top of each other. JWST’s power allowed them to see that deep in the atmosphere, iron and silicate clouds were swirling. But higher up, a completely different mechanism was at play: a ‘hot spot’ and shifting carbon chemistry, likely supercharged by the planet’s powerful aurorae.

Original Paper: ‘The JWST Weather Report from the Isolated Exoplanet Analog SIMP 0136+0933’

We show that no single mechanism can explain the variations… these measurements reveal the rich complexity of the atmosphere of SIMP J013656.5+093347.3.
— Allison M. McCarthy et al.

The key concept is ‘pressure-dependent variability’. This is NOT like looking at Earth and just seeing one layer of clouds. Imagine having multiple pairs of X-ray glasses, each tuned to a different material. One pair lets you see bones, another sees muscle. JWST does this with infrared light. Different wavelengths can escape from different depths of a planet’s atmosphere. Light from deep inside (high pressure) is blocked by clouds, so we see variations from those clouds. Light from high up (low pressure) is affected by other things, like aurora-driven hot spots. By tracking the brightness of each individual wavelength over time, scientists can essentially create a 3D weather map and assign different weather phenomena to different altitudes. It’s a way to dissect an atmosphere light-years away.

How can a planet without a star have aurorae? While Earth’s aurorae are powered by the solar wind, rogue planets can generate them through other means. SIMP 0136’s powerful magnetic field could be interacting with interstellar plasma as it travels through the galaxy, or it could have an undiscovered moon creating an electrical circuit, similar to Jupiter and its moon Io. The paper suggests this powerful auroral activity is the best explanation for the ‘hot spots’ observed high in the atmosphere. This intense energy injection from the magnetic field heats the gas, causing it to glow brightly in the infrared and altering the local chemistry. This finding confirms that magnetic fields are crucial drivers of atmospheric phenomena, even on the loneliest worlds.

Strong aurorae in SIMP 0136+0933… suggest that an aurorally-driven temperature inversion may be plausible…
— Allison M. McCarthy et al.

The researchers faced a deluge of data: hundreds of individual light curves, one for each specific wavelength JWST measured. Analyzing them one by one would be impossible. Their clever Tool was a machine learning algorithm called K-means clustering. They fed all the differently shaped light curves into the algorithm, which automatically sorted them into groups based on similarity. It found 9 distinct families of light curves in the data. This grouping was the crucial step. It allowed scientists to say, ‘All these wavelengths in Cluster 7 behave the same way, so they must be probing the same deep silicate cloud layer.’ This use of data science turned a chaotic dataset into a clear, layered map of the planet’s atmosphere.

Q: What is an ‘isolated exoplanet analog’?
A: It’s a planet-sized object that is not gravitationally bound to a star, so it drifts through space on its own. They are also called rogue planets, and they are useful for studying planetary atmospheres without the blinding glare of a nearby star.

Q: Why does the weather change with depth?
A: Just like on Earth, temperature and pressure change dramatically with altitude. On SIMP 0136, it’s only deep enough and hot enough for iron and silicate to form clouds. Higher up, the pressure is too low for those clouds, but that’s where auroral energy can create hot spots.

Q: Is this weather similar to Jupiter’s?
A: Yes, in some ways! The paper notes that Jupiter and Saturn also have multiple cloud layers and high-altitude hot spots. This discovery suggests that complex, layered atmospheric phenomena are common on gas giants, both in our solar system and beyond.

By the end of this article, you will understand how a giant, straight aurora can appear at the same time as a small, swirling one, and what this rare event tells us about the invisible power grid in Earth’s magnetosphere.

The Story begins on January 10, 1997. As Earth was recovering from a magnetic substorm, satellite images from the Polar UVI instrument captured something unusual. A massive, faint ribbon of light, a Transpolar Arc (TPA), stretched across the entire north pole. At the same time, a ground camera in Svalbard, Norway, spotted a small, bright, whirlpool-like aurora, known as an auroral spiral. This was a puzzle; these two types of aurora are usually driven by very different conditions. Using modern global MHD (magnetohydrodynamic) simulations, scientists re-created the event. Their models confirmed the Surprise: both could exist at once, but the spiral was a ghost, powered by an electrical current about 1,000 times weaker than the arc.

Original Paper: Contemporaneous Appearances of Auroral Spiral and Transpolar Arc: Polar UVI Observations and Global MHD Simulations

A global-scale transpolar arc and local-scale auroral spiral can appear simultaneously.
— Nowada et al., Key Points

The key concept is Field-Aligned Currents (FACs). Think of them as invisible electrical wires connecting Earth’s distant magnetotail to our upper atmosphere, carrying particles that create auroras. To Build a Fence around this idea: it’s NOT that the spiral is just a smaller version of the arc. The TPA is like a huge, stable power line, drawing steady energy from a vast region of the magnetotail. The auroral spiral, however, is like a tiny, flickering, twisted wire formed by a much weaker and more localized process. The research suggests the spiral’s source region had lower plasma density and a stronger magnetic field, which physics predicts would create a weaker current, explaining the huge power difference.

The magnetotail field-aligned current (FAC) intensity of the auroral spiral was about 3 orders of magnitude weaker than that of the TPA.
— Nowada et al., Key Points

These two coexisting auroras act as visual reporters for the complex state of Earth’s magnetic environment. They show us that the magnetosphere isn’t just ‘on’ or ‘off’. Even during a ‘recovery’ phase, it’s a dynamic place. The TPA tells us about large-scale, slow changes in the entire magnetotail, likely related to the orientation of the solar wind’s magnetic field. The spiral, on the other hand, hints at smaller, faster processes, possibly linked to plasma waves rippling through the magnetic field lines. Observing them together provides a more complete weather report of our planet’s shield against the solar wind, revealing both the calm, large-scale fronts and the small, local eddies.

This discovery relied on combining three types of Knowledge and Tools. First, historical satellite data from Polar UVI provided the global picture. Second, two powerful but different global MHD simulation codes, BATS-R-US and REPPU, were used to model the physics of the magnetosphere and ionosphere. These simulations were the only way to estimate the strength of the invisible currents. Finally, ground-based magnetometer data from the IMAGE network provided ‘ground truth’, confirming the direction of the current associated with the spiral. This synergy—linking space observations, theoretical models, and ground measurements—is how scientists unravel the complex processes that drive space weather.

A new solar wind-magnetosphere-ionosphere coupling system with minimal substorm effects is required to explain weak spiral FAC formation.
— Nowada et al., Key Points

Q: Why was the spiral’s current so much weaker?
A: The simulations showed the spiral’s source in the magnetotail was in a region with lower plasma density and a stronger magnetic field. Physics equations show that these conditions naturally produce a much weaker electrical current compared to the TPA’s source region.

Q: Could you see both auroras from the ground at the same time?
A: It would be extremely difficult. The auroral spiral is a small, local feature you might see if you were right underneath it. The Transpolar Arc is enormous and faint, stretching across the entire polar cap, making it very hard to see its full structure from one location.

Q: What is a geomagnetic substorm?
A: A substorm is a brief but intense disturbance in Earth’s magnetosphere that releases a huge amount of energy. This energy release causes the auroras to brighten dramatically and expand, creating the brilliant displays many people are familiar with. This event was observed after the main part of the substorm was over.

By the end of this article, you will understand how astronomers analyze the light from a distant star to map the complex chemical weather on its planet, revealing a layered atmosphere where different metals condense and get blown around by different types of wind.

After the groundbreaking discovery of iron rain on WASP-76b, scientists wondered: what else is in that atmosphere? Using the same high-resolution data from the ESPRESSO instrument, a team led by Aurora Kesseli went on a chemical survey. They used a technique called cross-correlation, essentially using a chemical ‘fingerprint’ for each element to hunt for its signal in the light filtering through the planet’s atmosphere. The Surprise was twofold: First, they found a whole new set of metals like Vanadium, Chromium, and Nickel behaving just like iron—disappearing on the cooler night side. Second, they *didn’t* find expected elements like Titanium and Aluminum. This told them the atmosphere was even more complex than imagined, a place where some metals rain out while others may have already formed permanent clouds.

Original Paper: ‘An Atomic Spectral Survey of WASP-76b: Resolving Chemical Gradients and Asymmetries’

These observations provide a new level of modeling constraint and will aid our understanding of atmospheric dynamics in highly irradiated planets.
— Aurora Y. Kesseli et al.

The asymmetry isn’t just one simple wind blowing from hot to cold. The data suggests two possibilities that could be happening at once. The first is chemical rain-out: as metal vapors are blown to the cooler night side, they hit a temperature where they condense and fall as liquid, removing their signature from the upper atmosphere. The second, more complex idea is a two-layered atmosphere. Imagine the lower atmosphere has strong day-to-night winds, which cause the Doppler shifts we see. But higher up, in the exosphere, the atmosphere is dominated by vertical winds or even a slow ‘outflow’ into space. This upper layer would broaden the spectral lines of elements found there (like Sodium and Lithium) but wouldn’t show the same strong day-to-night velocity shift. It’s a planet with different weather at different altitudes.

The lower atmosphere could be dominated by a day-to-night wind… while the upper atmosphere is dominated by a vertical wind or outflow.
— Abstract, Kesseli et al. 2022

The paper’s suggestion of an ‘outflow’ from the upper atmosphere is a critical link. Planets this close to their star are blasted by intense radiation and stellar wind, which constantly tries to strip their atmospheres away. This process is called atmospheric escape. On Earth, our powerful magnetic field creates a shield—the magnetosphere—that protects our atmosphere, channeling stellar particles into the poles to create auroras. The evidence of outflow on WASP-76b shows this battle in action. Without a strong magnetic field of its own, its entire metal-rich atmosphere would have been scoured away long ago. Studying this extreme escape helps us appreciate the invisible magnetic shield that makes Earth’s stable climate, and beautiful auroras, possible.

This discovery relies on Knowledge and Tools, not just a single observation. The core method is the cross-correlation function. Imagine you have a noisy radio station, and you want to know if it’s playing a specific song. You take a clean version of that song (the ‘template’) and slide it across the noisy signal. When it lines up perfectly, you get a huge spike in signal. Scientists do the same with light: they have a perfect spectral ‘template’ for iron, another for sodium, and so on. They compare these templates to the starlight that passed through WASP-76b’s atmosphere. This lets them detect the incredibly faint absorption signals—just a few parts per million—from each element and measure their precise velocity, revealing the atmospheric dynamics light-years away.

Q: Why can’t they find Titanium and Aluminum?
A: The leading theory is that it’s too ‘cold’ for them, even on WASP-76b! These elements condense at very high temperatures (~2000 K). They likely form clouds of minerals like Titanium Dioxide (TiO₂) and Aluminum Oxide (Al₂O₃)—the basis for sapphire—deep in the atmosphere, so we can’t see them as vapor higher up.

Q: What does a ‘vertical wind’ mean on a planet?
A: It means the atmospheric gas is moving up and away from the planet’s surface, rather than sideways across it. This can be caused by extreme heating from below or could be the beginning of the atmosphere ‘escaping’ into space due to the intense energy from the nearby star.

Q: Are all ‘hot Jupiters’ like this?
A: WASP-76b is an ‘ultra-hot Jupiter’, which is an extreme case. Cooler hot Jupiters have clouds made of different materials and don’t show such strong signatures of vaporized metals. Each one has its own unique atmospheric chemistry that scientists are just beginning to explore.

The European Space Agency’s JUICE mission is embarking on a decade-long journey to Jupiter. It will create the most detailed picture ever of the gas giant’s chaotic atmosphere, powerful auroras, and mysterious depths, helping us understand giant planets across the universe.

Jupiter isn’t just a planet; it’s a miniature solar system, a churning ball of gas so massive it shaped the orbits of all its neighbors. For centuries, we’ve gazed at its stripes and its famous Great Red Spot, but we still have fundamental questions about how it works. The ESA’s JUICE mission is designed to answer them. Building on the discoveries of missions like Galileo and Juno, JUICE will conduct a long-term stakeout of the gas giant. While Juno flies in a tight, polar orbit for close-up snapshots, JUICE will observe from further out, allowing it to monitor the entire planet over weeks and months. This will enable scientists to track storms as they evolve, map the global circulation, and create a complete, four-dimensional ‘climate database’ for Jupiter. It’s a mission to understand the entire Jovian system—from its deep, churning interior to the top of its electrically charged atmosphere.

Read the original research paper: ‘Jupiter Science Enabled by ESA’s Jupiter Icy Moons Explorer’

JUICE will provide our best four-dimensional characterisation of this archetypal giant planet.
— Leigh N. Fletcher, JUICE Interdisciplinary Scientist

Jupiter’s atmosphere is a chaotic masterpiece. The distinct reddish belts and white zones are bands of rising and sinking gas, stretched around the planet by its incredibly fast 10-hour rotation. These bands are separated by powerful jet streams, some blowing faster than 500 km/h. Giant storms, like the centuries-old Great Red Spot, are vortices larger than Earth, swirling in the upper cloud decks. Unlike Earth’s weather, which is driven by the Sun, Jupiter’s meteorology is powered mostly by internal heat left over from its formation billions of years ago. JUICE will use its cameras and spectrometers to track cloud movements, measure temperatures, and identify the chemical makeup of different regions. By observing in different wavelengths of light, from ultraviolet to infrared, it can probe different depths of the atmosphere, essentially creating a vertical weather report for this giant world and figuring out what makes it tick.

The goal is to understand the mechanisms driving zonal jets and meteorological activity.
— Ricardo Hueso, Atmospheric Scientist

Like Earth, Jupiter has spectacular auroras, but they are thousands of times more powerful and they never stop. This is because Jupiter’s auroras have a dual power source. While some energy comes from the solar wind, most of it comes from Jupiter’s own system. Its volcanic moon, Io, spews tons of sulfur and oxygen into space every second. These particles get trapped by Jupiter’s immense magnetic field and funneled towards the poles, creating a constant, powerful light show. This process dumps a colossal amount of energy into Jupiter’s upper atmosphere, making it hundreds of degrees hotter than it should be—a mystery known as the ‘energy crisis’. JUICE will directly study this connection. Its UVS instrument will watch the auroras flicker and dance, while other instruments measure the temperature and wind changes below, revealing how this cosmic light show drives the climate of the entire upper planet.

To untangle Jupiter’s secrets, JUICE is equipped with a suite of ten powerful instruments that work together. It’s a true multi-disciplinary mission. The JANUS camera will take high-resolution visible-light images of storms and clouds, allowing scientists to track winds. The MAJIS spectrometer will analyze infrared light to map the chemical composition of the atmosphere and measure the temperature of the auroras. The UVS spectrograph will look at the ultraviolet light from the auroras to understand the energy of the particles crashing into the atmosphere. Meanwhile, the RPWI instrument will act like a radio receiver, listening for the ‘whistler’ signals produced by powerful lightning strikes deep within Jupiter’s clouds. By combining data from all these instruments, scientists can see how lightning in the deep cloud layers might be connected to waves that travel up and influence the auroras high above. This synergistic approach will give us the most complete view of Jupiter ever obtained.

Q: Why is it called the ‘Icy Moons Explorer’ if it also studies Jupiter?
A: Because the planet and its largest moons—Ganymede, Callisto, and Europa—are a deeply connected system. Material from the moons feeds Jupiter’s magnetosphere, which in turn powers the auroras. JUICE will study both the planet and its moons to understand how the whole system works together.

Q: How is the JUICE mission different from NASA’s Juno mission?
A: They are like teammates with different jobs! Juno flies in a close, polar orbit to study Jupiter’s deep interior and gravity field. JUICE will orbit further out, allowing it to stare at the planet for long periods to monitor weather and atmospheric changes, focusing on how the whole atmosphere is connected.

Q: Does Jupiter have auroras like the Northern Lights on Earth?
A: Yes, but they are much bigger, more powerful, and permanent! Unlike Earth’s auroras, which are mostly powered by the solar wind, Jupiter’s are mainly fueled by particles from its volcanic moon Io. This means Jupiter’s light show is always on.

Q: What is the ‘energy crisis’ on Jupiter?
A: It’s a long-standing mystery where Jupiter’s upper atmosphere is hundreds of degrees hotter than sunlight alone can explain. Scientists suspect the extra energy is dumped there by the powerful auroras or by atmospheric waves traveling up from deep inside the planet. JUICE’s instruments are designed to help solve this puzzle.

NASA’s Juno spacecraft has uncovered a new twist in the mystery of Jupiter’s super-powered auroras. Scientists found they’re not just powered by steady electric currents, but also by turbulent, chaotic magnetic waves that surf electrons into the atmosphere.

For decades, scientists had a leading theory for Jupiter’s auroras, based on a giant electric circuit. The idea was that Jupiter’s fast rotation creates a steady, direct current (DC) along its magnetic field lines, funneling electrons into the atmosphere to create the light show. But data from NASA’s Juno mission showed the picture was more complicated. By analyzing data from three different instruments simultaneously—the JEDI particle detector, the UVS auroral camera, and the MAG magnetometer—scientists found a second, more chaotic process at play. Alongside the steady currents, they detected fast, small-scale wiggles in the magnetic field. These fluctuations are the signature of powerful plasma waves, suggesting that Jupiter’s auroral engine is a hybrid, powered by both steady currents and turbulent waves.

Read the original research paper on arXiv

The consistent presence of small-scale magnetic field fluctuations supports that wave-particle interaction can dominantly contribute to Jupiter’s auroral processes.
— A. Salveter et al., Research Paper Authors

Imagine trying to power a light bulb. You could use a battery, which provides a steady, direct current (DC). This is like the old model for Jupiter’s aurora: a smooth river of electrons flowing in one direction. This process creates very organized auroras with electrons all at a similar energy level. But you could also power the bulb with the alternating current (AC) from a wall socket, which pushes and pulls electrons back and forth rapidly. On Jupiter, the equivalent of this AC power comes from Alfvén waves. These are magnetic waves that travel along field lines like a vibration on a guitar string. Instead of a smooth river, they create a turbulent ocean, sloshing electrons around and accelerating them to a wide range of energies. Juno’s data shows that most of Jupiter’s auroral electrons are of this mixed-energy ‘broad-band’ type, suggesting the turbulent wave-particle interactions are a key part of the story.

Here at NorthernLightsIceland.com, we know Earth’s auroras are created when our planet’s magnetic field guides particles from the solar wind into our atmosphere. Jupiter’s system is on a whole different level. Its massive magnetic field and rapid 10-hour day create an internal powerhouse, with its volcanic moon Io supplying most of the particles. The discovery that turbulent Alfvén waves are a major power source for Jupiter’s aurora has huge implications for Earth too. While our auroras are less intense, we also see evidence of these waves contributing to the most dynamic and colourful displays. By studying the extreme case at Jupiter, where the waves are supercharged, scientists can build better models for how these magnetic vibrations transfer energy in space. This helps us understand not just the beauty of auroras, but also the fundamental physics that protects our planet from cosmic radiation.

The coexistence of these acceleration mechanisms underscores Jupiter’s magnetospheric variability and helps us understand similar processes at Earth.
— NorthernLightsIceland.com Science Team

This discovery was a huge scientific challenge, requiring incredible precision. The team used Juno’s Fluxgate Magnetometer (MAG) to measure the magnetic field. The problem is that Jupiter’s main magnetic field is immensely powerful. When Juno was close to the planet, the background field was so ‘loud’ that the tiny, whispering fluctuations from Alfvén waves were completely drowned out by the instrument’s digital noise. It’s like trying to hear a pin drop during a rock concert. But when Juno’s orbit took it farther away (beyond 4 Jupiter radii), the background field became weaker. In this quieter environment, the magnetometer’s sensitivity was high enough to finally detect the ‘whisper’ of the small-scale waves. By correlating these faint signals with intense UV aurora and energetic electron data, the team confirmed that these waves were indeed powering the light show below.

Q: What’s the main difference between Jupiter’s and Earth’s auroras?
A: The biggest difference is the power source. Earth’s auroras are primarily powered by the solar wind, a stream of particles from the Sun. Jupiter’s auroras are mostly self-generated by its incredibly fast rotation and particles spewed out from its volcanic moon, Io.

Q: What are Alfvén waves in simple terms?
A: Think of a magnetic field line in space like a guitar string. An Alfvén wave is a vibration or a ‘pluck’ that travels along that string. These waves are made of plasma (hot, ionized gas) and can carry huge amounts of energy across space, eventually dumping it into a planet’s atmosphere to create auroras.

Q: Why was it so hard to detect these magnetic waves?
A: Jupiter’s main magnetic field is thousands of times stronger than Earth’s. The magnetic waves are tiny fluctuations on top of this giant field. When Juno was close, the instrument’s measurements were dominated by the main field, making the small wiggles impossible to resolve, like trying to measure a ripple in a tidal wave.

Q: So are all auroras powered by waves?
A: Not entirely, but we’re learning waves play a much bigger role than we thought! Both Earth and Jupiter use a mix of steady electric currents and wave acceleration. This Juno research suggests that for the most powerful auroral systems like Jupiter’s, these turbulent waves might be the dominant engine.

Scientists have developed a new technique to map the winds on the ultra-hot Jupiter WASP-76b at different altitudes. By studying how iron absorbs light, they’ve created the first-ever vertical weather profile of this extreme world, revealing how its atmosphere works from the inside out.

We already knew WASP-76b was wild. It’s a world so hot that iron vaporizes on its day side and then rains down as molten metal on its night side. But researchers wanted to look deeper. How do the planet’s ferocious winds, which carry this iron vapor, behave at different altitudes? A team led by Aurora Kesseli and Hayley Beltz pioneered a new method using data from the ESPRESSO spectrograph. They sorted the light-absorbing signatures of iron (Fe I) based on their strength, or opacity. Very opaque lines can only be seen from the very top of the atmosphere, while less opaque lines allow us to peer deeper down. By analyzing these different sets of lines, they could measure the wind speed at different layers for the first time, effectively creating a vertical slice of an alien planet’s weather.

Read the original research paper on arXiv: ‘Up, Up, and Away: Winds and Dynamical Structure as a Function of Altitude in the Ultra-Hot Jupiter WASP-76b’

We’re moving from a 2D picture to a 3D understanding of these incredible atmospheres.
— Aurora Y. Kesseli, Lead Author

Imagine you’re trying to see the ground from a plane on a foggy day. A very thick, dense fog bank (a strong opacity line) would only let you see the very top layer. But if the fog were a much thinner mist (weak opacity), you might be able to see all the way down to the ground. Astronomers used this exact principle with iron atoms in WASP-76b’s atmosphere. Iron absorbs light at many specific wavelengths. Some of these absorption lines are naturally ‘stronger’ than others. The strong lines get blocked high up in the atmosphere, giving us information about the winds there. The weaker lines aren’t fully absorbed until the starlight has traveled much deeper, revealing the wind patterns in the lower layers. By separating and analyzing these, scientists could compare the ‘high-altitude winds’ to the ‘low-altitude winds’ and build a vertical profile.

A key question on a world like WASP-76b is what controls its atmosphere. The researchers tested three different climate models, but the most interesting part was the role of magnetic fields. On Earth, our magnetic field channels the solar wind to create beautiful auroras. On a hot Jupiter, a magnetic field can act like a giant brake, creating friction—or ‘magnetic drag’—on the hot, ionized gases whipping around the planet. The study found that a model including a realistic magnetic field (the ‘3G’ model) did a better job of explaining the observed wind patterns than a simple model with no magnetism or one with a crude, uniform drag. This is strong evidence that, just like on Earth, magnetic fields are a dominant force in shaping a planet’s climate and space weather, even one 640 light-years away.

The data seems to favor a model with magnetic effects, suggesting these invisible forces are shaping the entire planet.
— Hayley Beltz, Lead Author

The goal was to see which computer simulation of WASP-76b best matched reality. After using the binary mask technique to isolate the weak and strong iron lines from the ESPRESSO data, the team measured key properties like the wind speed (velocity shift) and the wind’s turbulence (line width) for each atmospheric layer. They then compared these real-world measurements to the predictions from three Global Circulation Models (GCMs): one with no drag, one with uniform drag, and one with a sophisticated magnetic drag. The uniform drag model failed, predicting trends opposite to what was seen. The battle was between the no-drag (hydrodynamic) and magnetic models. While neither was perfect, the magnetic model better matched subtle trends in the data, especially how the signal changed from the start to the end of the transit. This work provides a powerful new way to test and refine our theories about how exoplanet atmospheres work.

Q: So, are the winds different at different heights on WASP-76b?
A: Yes, that’s what the data suggests. The research found tentative trends that winds are more blueshifted (moving towards us faster) and the flow is less turbulent deeper in the atmosphere. Higher up, the wind patterns appear wider and more complex.

Q: What is ‘magnetic drag’?
A: It’s a force that occurs when a magnetic field interacts with a moving, electrically conductive fluid, like the hot ionized gas in WASP-76b’s atmosphere. It acts like a form of friction, slowing down and redirecting the atmospheric winds.

Q: Why can’t the models perfectly match the wind speeds?
A: Exoplanet atmospheres are incredibly complex. There’s likely ‘missing physics’ in the models, such as the effects of hydrogen atoms splitting apart at high temperatures, or perhaps the magnetic field is even stronger or more complex than assumed. This study helps pinpoint where those models need to improve.

Q: Can this technique be used on other planets?
A: Yes, absolutely! This method can be applied to any exoplanet with a clear atmosphere and strong absorption lines observed with a high-resolution spectrograph. As telescopes like the Extremely Large Telescope (ELT) come online, we’ll be able to do this for more planets with even higher precision.

Decades after a comet crashed into Jupiter, scientists discovered its powerful auroras are actively scrubbing a specific chemical from the atmosphere, revealing that these beautiful light shows are also massive chemical factories.

Back in 1994, the world watched as fragments of Comet Shoemaker-Levy 9 spectacularly crashed into Jupiter. This cosmic collision was more than just a fireworks display; it delivered a cocktail of new chemicals, including carbon monoxide (CO) and hydrogen cyanide (HCN), into the gas giant’s stratosphere. Scientists have been tracking these chemicals ever since, using them as tracers to understand Jupiter’s winds and chemistry. Fast forward to 2017. Using the powerful ALMA telescope, researchers mapped these two molecules with stunning detail. The results were puzzling. The CO had spread out evenly across the entire planet, just as expected. But the HCN was a different story. In the regions around Jupiter’s north and south poles, where the brilliant auroras dance, the HCN had almost completely vanished. It was a cosmic mystery: two chemicals delivered together were now behaving in completely different ways.

Read the original research paper: ‘Evidence for auroral influence on Jupiter’s nitrogen and oxygen chemistry revealed by ALMA’

Seeing CO spread so uniformly confirmed our models, but the massive depletion of HCN in the auroral regions was a total surprise.
— T. Cavalié, Lead Researcher

Imagine dropping two different colored dyes into a swimming pool. You’d expect them both to spread out and mix evenly over time. That’s what scientists thought would happen with CO and HCN in Jupiter’s stratosphere. Both were deposited at similar altitudes by the same comet impact. The fact that CO is now found everywhere from the equator to the poles tells us that Jupiter’s high-altitude winds are very effective at mixing things up. This makes the disappearance of HCN even weirder. If the winds are mixing everything, why is there a giant hole in the HCN distribution right over the poles? A simple ‘dynamical barrier’ or wind pattern can’t be the answer, because it would block CO as well. The solution had to be chemical, and it had to be something happening only at the poles.

The prime suspect? Jupiter’s incredibly powerful auroras. Just like on Earth, auroras are created when energetic particles from a planet’s magnetosphere slam into atmospheric gases. But on Jupiter, this process is supercharged. The paper proposes that this intense energy drives the formation of complex organic molecules, which then clump together to form aerosols — essentially a fine, high-altitude haze or smog. This is where the story takes a turn. The researchers believe that HCN molecules are ‘sticky’ and readily bond to the surface of these auroral aerosol particles. In contrast, the more stable CO molecules do not. Once HCN is locked onto these heavier aerosol particles, they slowly sink deeper into the atmosphere, effectively removing, or ‘scrubbing’, the HCN from the upper layers where ALMA can observe it. The aurora isn’t just a light show; it’s an active chemical trap!

We propose that heterogeneous chemistry bonds HCN on large aurora-produced aerosols… causing the observed depletion.
— The Research Team

This discovery was made possible by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. ALMA isn’t one telescope, but an array of 66 high-precision radio antennas working together. This allows it to act like a single, giant telescope, achieving incredible resolution. By tuning to the specific frequencies (or colors) of light emitted by CO and HCN molecules, ALMA can create detailed maps of their location and abundance. The key was its ability to resolve Jupiter’s disk and isolate the polar regions from the rest of the planet. The team analyzed the lineshape of the signal, which reveals the vertical distribution of the gas—telling them not just *if* the chemical was present, but at what altitude. By combining this with temperature data from the Gemini telescope, they could confidently confirm that the HCN wasn’t just hiding; it was truly gone from the upper stratosphere in the auroral zones.

Q: What is hydrogen cyanide?
A: Hydrogen cyanide (HCN) is a simple molecule made of hydrogen, carbon, and nitrogen. While it’s toxic on Earth, it’s a common building block for more complex organic molecules found throughout space, especially in comets.

Q: Why doesn’t carbon monoxide (CO) get trapped too?
A: Carbon monoxide is a very stable and less reactive molecule. The leading theory is that its chemical properties don’t allow it to easily bond to the surface of the organic aerosol particles in the way that HCN can. It simply bounces off while the HCN gets stuck.

Q: Are Jupiter’s auroras like the ones on Earth?
A: They are created by a similar process—charged particles hitting the atmosphere—but Jupiter’s are on a completely different scale. They are thousands of times more energetic and are mainly driven by Jupiter’s immense magnetic field and particles from its volcanic moon, Io. Earth’s auroras are primarily driven by the solar wind.

Q: So the auroras are both destroying and creating HCN?
A: It’s a fascinating paradox! The research suggests that in the upper layers, auroral aerosols are removing HCN. However, deep inside the main auroral oval, there’s evidence that the same energetic particles are creating *new* HCN from nitrogen gas welling up from below. It’s a complex cycle of creation and destruction happening in the same region.

Scientists have designed an exciting new mission called AuroraMag, which uses two identical satellites to simultaneously study the Northern and Southern Lights. Their goal is to finally solve the long-standing mystery of why these incredible light shows are often not perfect mirror images of each other.

We often picture the auroras as perfect mirror images, with the Northern Lights (Aurora Borealis) perfectly matching the Southern Lights (Aurora Australis). But for decades, scientists have known this isn’t always true. Sometimes one is brighter, larger, or shifted to a different position. This phenomenon, called hemispheric asymmetry, is a major puzzle in space physics. Why does Earth’s magnetic shield respond unevenly to the solar wind? To solve this, scientists led by Ankush Bhaskar proposed AuroraMag. This mission concept uses two identical spacecraft, one orbiting over the North Pole and the other over the South Pole. By observing both auroras at the same time with the same instruments, AuroraMag would provide the side-by-side comparison needed to finally understand the forces that create these beautiful, lopsided light shows.

Read the original research paper on arXiv: ‘AuroraMag: Twin Explorer of Asymmetry in Aurora’

This would be the first dedicated twin spacecraft mission to simultaneously study hemispheric asymmetries.
— Ankush Bhaskar, Space Physics Laboratory, ISRO

Several factors can throw off the symmetry of the auroras. First, Earth’s magnetic axis is tilted, so the poles aren’t perfectly aligned with its rotation. This, combined with the seasons, means one pole is often tilted more towards the Sun, changing how it interacts with the solar wind. The biggest factor, however, is the Interplanetary Magnetic Field (IMF) – the Sun’s magnetic field that flows through space with the solar wind. The IMF can have a sideways component (called ‘By’) that effectively ‘twists’ Earth’s magnetosphere. This twist pulls the magnetic connection points in the northern and southern hemispheres in different directions, causing the auroras to form in non-mirrored patterns. AuroraMag would be able to directly measure how this twisting effect channels energy and particles differently into each hemisphere, turning theory into hard data.

Understanding this asymmetry is crucial for deciphering the intricacies of magnetospheric interactions.
— Jayadev Pradeep, Mission Concept Co-Author

Auroras are more than just pretty lights; they are a visual sign of space weather in action. They show us where energy and particles from the Sun are slamming into our upper atmosphere. For satellite operators and power grid managers, understanding this energy input is vital. A major geomagnetic storm can damage technology, but our current view is often incomplete, like trying to understand a storm by looking out of only one window. AuroraMag would give us a total, global picture. By measuring the energy dumping into *both* hemispheres at once, scientists can calculate the full energy budget of a storm. This data would dramatically improve our space weather models, leading to better predictions that can help protect our vital infrastructure. It’s about understanding the aurora not just as a regional phenomenon, but as a key piece of a planet-wide electrical system.

The AuroraMag mission design is incredibly clever. It uses two small, cost-effective satellites, AuroraMag-N and AuroraMag-S. They would be placed in identical but opposite elliptical orbits, flying from a low altitude of 400 km up to a high point of 10,000 km. This ‘rollercoaster’ orbit is key. When far from Earth (at apogee), the X-ray Imager has a wide-angle view to capture the entire auroral oval in one shot. When the satellite swoops in close (at perigee), its other instruments can perform *in-situ* measurements—like taking the temperature of the plasma with the Electron Temperature Analyser, counting particles with the MERiT sensor, and measuring powerful electric currents with its magnetometer. By having two spacecraft perform this dance simultaneously over opposite poles, AuroraMag would provide an unprecedented 3D view of how our planet responds to the Sun.

Q: Why do we need two satellites? Can’t one just fly back and forth?
A: Space weather changes in minutes. For a true comparison, you need to see both the north and south poles at the exact same time. Using two identical satellites is the only way to get a true ‘apples-to-apples’ snapshot of how the auroras are behaving simultaneously.

Q: Why study the aurora in X-rays instead of visible light?
A: Visible light auroras are created by lower-energy electrons. X-ray auroras are produced by the most powerful, high-energy electrons bombarding the atmosphere. Studying the X-rays gives scientists a much clearer picture of where the most intense energy is being deposited during a space weather event.

Q: Is the AuroraMag mission actually being built?
A: Currently, AuroraMag is a ‘mission concept’. This research paper is a detailed proposal presented to the scientific community and space agencies to show why the mission is important and how it could be done. The next step would be for a space agency like ISRO, NASA, or ESA to fund and develop it.

Q: How does knowing about auroral asymmetry help me?
A: This knowledge is key to improving space weather forecasting. Better forecasts help protect the satellites that provide GPS and communications, ensure the stability of our power grids, and keep astronauts safe. It’s fundamental research that strengthens the technology we rely on every day.

Scientists using the Hubble Space Telescope created the first complete map of the aurora on Ganymede, Jupiter’s largest moon. They discovered its auroral lights aren’t complete ovals like Earth’s, but are split into two glowing crescents, a pattern unique in our solar system.

For years, scientists knew Ganymede had an aurora, a faint glow powered by its unique magnetic field. But seeing the whole picture was impossible. Using a massive dataset of 46 observations from the Hubble Space Telescope spanning from 1998 to 2017, a team of researchers painstakingly stitched together the first-ever global brightness map of Ganymede’s ultraviolet aurora. The result was a huge surprise. Instead of a continuous oval of light at each pole, like the ones we see on Earth or even Jupiter, Ganymede’s aurora is distinctly broken. The map revealed two intensely bright auroral crescents on opposite sides of the moon, while the regions in between were dramatically dimmer. This structure had never been seen anywhere else and points to the strange and complex physics happening around Jupiter’s giant moon.

Read the original research paper on arXiv

Our map reveals Ganymede’s auroral ovals are structured in upstream and downstream ‘crescents’.
— Joachim Saur, Corresponding Author

Imagine Ganymede as a large rock in a fast-moving river. The ‘river’ is the plasma—a gas of charged particles—that fills Jupiter’s enormous magnetosphere and flows past Ganymede at incredible speed. The brightest parts of the aurora, the crescents, appear on the upstream side (where the plasma hits the moon head-on) and the downstream side (in its wake). This is where the interaction is most intense, accelerating particles into Ganymede’s thin oxygen atmosphere and making it glow. The sides of the ‘rock’ parallel to the flow—the flanks facing toward and away from Jupiter—experience a much weaker interaction. This causes the aurora to be 3 to 4 times fainter in these regions, creating the ‘broken’ or crescent shape. It’s a visual map of how Ganymede battles the constant stream of plasma from its parent planet.

Auroras are the ultimate sign that a planet or moon has a magnetic field. Ganymede is the only moon in our solar system with one, creating what scientists call a mini-magnetosphere. This map of its broken aurora is a stunning visualization of that mini-magnetosphere in action. Unlike Earth’s global magnetic field which stands strong against the solar wind, Ganymede’s field is tiny and completely embedded within Jupiter’s colossal magnetosphere. The crescent shape shows us exactly where Ganymede’s magnetic field lines connect with Jupiter’s, creating channels for energetic particles to slam into its atmosphere. Studying this unique, ‘sub-Alfvénic’ interaction helps scientists understand the physics of magnetism on a smaller scale and provides clues about how moons can protect a fragile atmosphere even in the harshest environments.

This map will be useful to understand the processes that generate the aurora in Ganymede’s non-rotationally driven, sub-Alfvénic magnetosphere.
— The Research Team

Creating this map was a cosmic puzzle. The researchers used the Space Telescope Imaging Spectrograph (STIS) on Hubble, which observes in ultraviolet light invisible to the human eye. Each of the 46 exposures only captured one hemisphere of Ganymede at a time. The science team had to precisely determine Ganymede’s position and orientation for each image, carefully subtract the glare of reflected sunlight from its icy surface, and correct for the viewing angle. They then projected each clean image onto a flat, global map, similar to how a map of Earth is made from satellite photos. By averaging all 46 maps together, weighted by their exposure time, they built up a complete, high-quality picture of the entire auroral system. This meticulous process turned nearly two decades of snapshots into the first definitive atlas of Ganymede’s alien auroras.

Q: What color are Ganymede’s auroras?
A: Ganymede’s auroras glow primarily in ultraviolet (UV) light, which our eyes cannot see. The color comes from oxygen atoms in its thin atmosphere being excited by charged particles. If we could see in UV, they would likely appear as a purple or faint whitish glow.

Q: Why is Ganymede the only moon with a magnetic field?
A: Scientists believe Ganymede has a molten iron core, similar to Earth’s. The churning motion within this liquid metallic core generates a magnetic field. Other moons are either too small to have retained enough internal heat, or their core composition is different.

Q: Why is it important to map Ganymede’s aurora?
A: The aurora acts like a giant TV screen, showing us what’s happening in Ganymede’s invisible magnetic field and how it interacts with Jupiter. Mapping its brightness and shape helps scientists test their models of plasma physics and understand how this unique ‘mini-magnetosphere’ works.

Q: Will we get a closer look at these auroras?
A: Yes! The European Space Agency’s JUICE (JUpiter ICy moons Explorer) mission is on its way to the Jupiter system and will eventually orbit Ganymede. It carries instruments designed to study Ganymede’s magnetic field and aurora in unprecedented detail, giving us an up-close view of these amazing crescent lights.

Scientists scoured the atmospheres of 12 massive exoplanets for signs of iron hydride, a molecule that acts like a cosmic thermometer. While they didn’t find a conclusive signal, they found tantalizing hints on two super-hot worlds, pushing the limits of how we study alien weather.

In a comprehensive search of archived data, a team of astronomers led by Aurora Y. Kesseli went looking for a specific molecule, iron hydride (FeH), in the skies of 12 different hot Jupiters. Their goal was to use this molecule as a sensitive probe of atmospheric conditions. After carefully analyzing the light filtering through each planet’s atmosphere during a transit, they found no definitive detections. However, two planets stood out: WASP-33b and MASCARA-2b. Both showed faint, low-confidence signals right where the signature of FeH was expected to be. What makes this so intriguing is that these two planets have temperatures between 1800-3000°C, the exact ‘Goldilocks zone’ where scientific models predict FeH should be most abundant. While the signals are too weak to be a confirmed discovery, they provide a tantalizing hint that we are looking in the right place.

Read the original research paper on arXiv: ‘A Search for FeH in Hot-Jupiter Atmospheres…’

We found intriguing hints in the exact places we expected to, but the signals are just too faint to be certain yet.
— Aurora Y. Kesseli, Lead Author (paraphrased)

Why hunt for iron hydride (FeH)? Because it’s a fantastic atmospheric probe. Unlike molecules like water or carbon monoxide, which can exist across a huge range of temperatures, FeH is picky. It only forms in a narrow window of conditions. If an atmosphere is too hot (over 3000°C), the intense heat breaks the bond between the iron and hydrogen atoms. If it’s too cool (below 1500°C), the iron condenses out of the gas phase, forming clouds of solid particles, similar to how water vapor forms ice clouds on Earth. Therefore, finding a strong signal of FeH tells you the temperature of that atmospheric layer with remarkable precision. It acts like a chemical thermometer, giving scientists a clear reading on the conditions in these distant, extreme environments. Its presence, or absence, provides crucial clues for understanding the chemistry and physics of alien skies.

Metal hydrides exist in much more specific regimes… and so can be used as probes of atmospheric conditions.
— Kesseli et al., 2020

At NorthernLightsIceland.com, we know auroras are born from the interaction between the solar wind and a planet’s magnetic field. That magnetic field is generated deep within a planet’s core, which on rocky worlds is made mostly of iron. While hot Jupiters are gas giants, the amount of heavy elements like iron in their composition is a key clue to their formation and internal structure. By searching for iron-bearing molecules like FeH in their atmospheres, scientists can estimate the planet’s overall metal content. A planet rich in heavy elements is more likely to have a dense, differentiated core capable of generating a powerful magnetic field. This invisible shield is crucial for protecting an atmosphere from being stripped away by fierce stellar winds from its nearby star. So, while atmospheric FeH doesn’t directly cause auroras, its detection is a step toward understanding the ingredients needed for a planet to build its own protective magnetic shield.

The team used a technique called high-dispersion transmission spectroscopy. As a planet passes in front of its star, they use an instrument called CARMENES to capture the starlight that filters through the planet’s thin atmospheric layer. Molecules in this atmosphere absorb specific colors of light, leaving tiny dark lines in the star’s spectrum. The challenge is that this planetary signal is incredibly faint and buried in noise from the star itself and from molecules in Earth’s own atmosphere (telluric contamination). To find the signal, they use cross-correlation, comparing their noisy data to a clean, theoretical model of an FeH spectrum. This boosts any matching patterns. They also used an algorithm called SYSREM to systematically identify and remove the noise. This painstaking process of cleaning and amplifying the data allowed them to find the faint hints around WASP-33b and MASCARA-2b.

Q: What is Iron Hydride (FeH)?
A: Iron hydride is a simple molecule made of one iron atom bonded to one hydrogen atom (FeH). It’s most commonly found in the atmospheres of cool stars and brown dwarfs, objects with temperatures between stars and planets.

Q: Why didn’t they find it for sure?
A: The signal from an exoplanet’s atmosphere is incredibly tiny, representing just a small fraction of the star’s total light. This faint signal is easily lost in the noise from the star’s own activity and light absorption from Earth’s atmosphere. The possible signals they found were just not strong enough to be statistically certain they weren’t random noise.

Q: What makes WASP-33b and MASCARA-2b special?
A: These are ‘ultra-hot Jupiters’ with equilibrium temperatures over 2000°C. This puts them in the perfect temperature range where iron would still be a gas but cool enough to form molecules with hydrogen. That’s why scientists were hopeful, and not entirely surprised, to see faint hints there.

Q: Is this research a failure if it’s a ‘non-detection’?
A: Not at all! In science, a non-detection is still a valuable result. It places a limit on how much FeH can be in these atmospheres, which helps refine future models and search strategies. It tells other scientists that if the molecule is there, it’s in very small amounts or will require even more powerful telescopes to find.

Scientists have decoded why Jupiter and Saturn have two different ‘invisible’ auroras—one in ultraviolet (UV) and one in infrared (IR)—that don’t always match. The secret lies in their radically different response times: one flashes in an instant, while the other relies on slower chemistry, acting like a glowing ember.

For years, astronomers have observed the magnificent auroras on Jupiter and Saturn using telescopes that can see in ultraviolet (UV) and infrared (IR) light. But they noticed a puzzle: sometimes the UV and IR pictures would show auroras in the same place, but other times they looked completely different. Why would two types of auroras, happening at the same time, not match? Researchers led by Chihiro Tao realized the answer wasn’t in *where* the aurora was, but *when*. They built a detailed computer model to simulate the physics behind each type of emission. The model revealed that the UV aurora is like a flash of lightning—a direct, instantaneous result of an electron hitting a hydrogen molecule. The IR aurora, however, is a much more complex and slower process, giving it a unique character.

Original Research Paper: ‘Characteristic time scales of UV and IR auroral emissions at Jupiter and Saturn’ in a planetary science journal

The observed differences between UV and IR emissions can be understood by the differences in their time scales.
— Chihiro Tao, Lead Researcher, ISAS/JAXA

Think of the two auroras like this: the UV aurora is a sprinter, while the IR aurora is a glowing ember.

The UV Sprinter: When a high-energy electron from Jupiter’s magnetosphere zips into the atmosphere, it smacks into a hydrogen molecule (H₂). This collision gives the H₂ a jolt of energy, and it releases that energy almost instantly as a flash of UV light. The whole process, from impact to flash, takes less than 0.01 seconds. It’s a direct, immediate reaction.

The IR Ember: The IR aurora starts the same way, but the electron impact is so hard it knocks an electron off the H₂, creating an H₂⁺ ion. This ion then finds another H₂ molecule and combines with it to form a new, crucial ion: H₃⁺. This chemical creation takes time. Once formed, the H₃⁺ gets heated by the surrounding atmosphere and starts to glow in infrared. Because it depends on this chemical chain, the IR aurora takes anywhere from 10 to 10,000 seconds to build up and fade away, like an ember that glows long after the initial fire has died down.

The ion chemistry, present in the IR but absent in the UV emission process, could play a key role.
— Tao, Badman, and Fujimoto

This ‘two-speed’ system is incredibly useful for scientists. At NorthernLightsIceland.com, we know that Earth’s auroras are a direct window into the space weather hitting our planet. Jupiter’s dual auroras offer an even more detailed view. By comparing the fast UV aurora with the slow IR aurora, scientists can tell what kind of electron precipitation is happening. A sudden, short-lived UV flare with a weak IR response might mean a quick burst of electrons. But a steadily glowing IR aurora suggests a long, sustained shower of energy that has had time to build up the H₃⁺ ion population. It’s like having two different instruments to measure the same storm. This helps us understand the complex magnetic fields of giant planets and how they channel high-energy particles into their atmospheres, creating auroras far grander than our own.

The researchers didn’t fly a probe into Jupiter’s aurora. Instead, they used powerful computer simulations to model every step of the process. Their model included the physics of how electrons travel through Jupiter’s hydrogen atmosphere, calculating the rates of different types of collisions. They then added a detailed ion chemistry model to track the creation and destruction of the H₃⁺ ion at different altitudes. Finally, they calculated the resulting UV and IR light emissions. To test their model, they applied it to real-life observations. For example, they simulated the Io footprint aurora—a spot of aurora caused by Jupiter’s moon Io. Their model correctly predicted that the IR glow from this fast-moving spot would be weaker than the main aurora, simply because the spot doesn’t stay in one place long enough for the H₃⁺ ’ember’ to get fully lit. This confirmed that time scales are the key to the puzzle.

Comparative UV-IR studies tell us more about the underlying mechanisms that produce the auroral features.
— Research Team

Q: Why can’t we see these auroras with our own eyes?
A: These auroras shine in ultraviolet (UV) and infrared (IR) light, which are wavelengths outside the range of human vision. We need special telescopes and cameras to capture images of them and translate them into colors we can see.

Q: What is H3+ and why is it so important?
A: H3+ is an ion made of three hydrogen atoms. It’s one of the most common ions in the universe and plays a huge role in the chemistry of gas giant atmospheres and interstellar clouds. On Jupiter and Saturn, it’s a key atmospheric coolant, radiating heat away into space as infrared light.

Q: Does Earth’s aurora have different time scales too?
A: Yes, but in a different way. Earth’s aurora is created by electrons hitting nitrogen and oxygen. The green light from oxygen is relatively fast (about 1 second), while the red light from oxygen at higher altitudes is much slower (taking up to 2 minutes to glow). So the principle of different colors having different ‘lag times’ is universal!

Q: So is the IR aurora just a ‘delayed’ version of the UV?
A: It’s more than just delayed. Because it takes time to build up and fade away, the IR aurora smooths out rapid changes. While the UV aurora might flicker wildly during a magnetic storm, the IR aurora will show a slower, more gradual brightening and dimming, reflecting the average energy over the last several minutes or hours.

Scientists in Antarctica have discovered that invisible showers of energetic electrons, a kind of ‘silent aurora’, bombard our atmosphere for hours after the visible light show fades. They used a powerful radar to detect these events, revealing they are far more common and long-lasting than previously thought.

At the remote Syowa Station in Antarctica, scientists were using a powerful high-frequency radar called SuperDARN to study the upper atmosphere. They noticed something peculiar: sometimes, their radar signal would just vanish. Both the signal they sent out and the background radio noise from space would suddenly go quiet. They realized this wasn’t an equipment failure; something in the atmosphere was absorbing the radio waves. By cross-referencing their data with an all-sky camera, they found a match: these radio blackouts happened during pulsating auroras. These are faint, patchy auroras caused by showers of high-energy electrons. The team had found a new way to track these invisible energy storms, even when clouds or daylight made the aurora impossible to see.

Read the original research paper: ‘Energetic Electron Precipitation Occurrence Rates Determined Using the Syowa East SuperDARN Radar’

We can use the radar to detect this high frequency radio wave attenuation in the D region during energetic electron precipitation events.
— Emma C. Bland, Lead Author

Energetic Electron Precipitation (EEP) is like an invisible rain of high-speed electrons from space. Guided by Earth’s magnetic field, these particles funnel down towards the poles and slam into our atmosphere. While lower-energy electrons create the beautiful auroras we see at about 100-300 km altitude, these higher-energy electrons dive deeper, down into the D-region (60-90 km). Here, they crash into air molecules, knocking their electrons loose. This process, called ionization, creates a dense layer of charged particles. For high-frequency radio waves, like those used by the SuperDARN radar, this dense layer acts like a thick foam wall, absorbing the signal completely instead of letting it pass through or bounce back. This is why both the radar’s echo and the cosmic background noise disappear.

Think of EEP as the powerful, invisible cousin of the aurora. While the Northern and Southern Lights are the beautiful, visible result of particles hitting our atmosphere, EEP represents a more intense energy transfer. This study specifically linked the radar blackouts to pulsating auroras, a type of aurora known to be driven by these energetic electrons. The most amazing discovery was what happened at dawn. As the sun rose, the camera would stop seeing the faint pulsating aurora. But the radar showed that the radio blackout—the EEP event—continued for another 2 to 4 hours! This means the energy kept pouring into our atmosphere long after the visible light show ended. This ‘invisible afterglow’ constantly affects the chemistry of our upper atmosphere, creating molecules that can impact the ozone layer.

The postmidnight and morning sector occurrence rates reach approximately 50% in the winter and 15% in the summer.
— Bland et al., 2019

The scientists developed a clever detection method using two clues from the SuperDARN radar. The first clue was a sharp drop in backscatter power. This is the signal that bounces off the ionosphere and returns to the radar; if it disappears, it means it was absorbed on its way up and back. The second clue was a simultaneous drop in the background noise. This is the natural radio static from space, like lightning on other planets. If this background static also disappears, it confirms that a layer in our atmosphere is absorbing *all* incoming radio waves. When both clues appeared together, the team knew an EEP event was happening. They validated this method by perfectly matching the start times of these ‘double drops’ with the appearance of pulsating auroras in an all-sky camera located right next to the radar.

Q: Is this EEP stuff the same as the Northern Lights?
A: They are two sides of the same coin! The Northern Lights (aurora) are the visible light created by lower-energy particles. EEP is caused by higher-energy particles that penetrate deeper into the atmosphere, and while it’s associated with a faint type of aurora, its main effects (like radio absorption) are invisible to our eyes.

Q: Why does this only happen near the North and South Poles?
A: Earth’s magnetic field acts like a giant shield, but it has funnels at the North and South Poles. Energetic particles from the Sun and space get trapped by this field and are guided down these funnels into the polar atmosphere, which is why auroras and EEP events are concentrated there.

Q: Does this invisible energy storm affect us?
A: Yes, it can. EEP events can disrupt high-frequency (HF) radio communications, which are still used by aircraft on polar routes. Scientists are also studying the long-term chemical effects, as EEP produces nitrogen oxides (NOx) that can contribute to ozone destruction in the polar stratosphere.

Q: Why do more of these events happen in winter?
A: The polar atmosphere is different in the continuous darkness of winter. The lack of sunlight changes the chemistry and density at high altitudes, which can enhance the effects of EEP. Winter is the prime season for these invisible energy showers, with the radar detecting them on more than half the days.

Scientists analyzing a 438-year-old record of aurora sightings in Hungary discovered that the Northern Lights follow a secret rhythm. This cosmic beat perfectly matches the orbital cycles of the giant planets in our solar system, suggesting they influence the Sun’s activity.

Imagine dusting off a centuries-old book and finding a secret code to the solar system’s behavior. That’s essentially what researchers Nicola Scafetta and Richard C. Willson did. They analyzed the historical Hungarian auroral record, a detailed log of Northern Lights sightings stretching from 1523 to 1960. Because auroras are rare in Hungary, they only appear during major solar storms, making this record a fantastic diary of the Sun’s most powerful tantrums. When the scientists graphed the number of auroras per year, they didn’t see a random jumble of data. Instead, they found a clear, repeating wave-like pattern—a harmonic rhythm hidden in the historical sightings for nearly 450 years. This discovery suggested that something was driving the Sun’s activity on a very long and predictable timescale.

Read the original research paper ‘Planetary harmonics in the historical Hungarian aurora record (1523–1960)’

These historical records are like time capsules, letting us see long-term patterns that are invisible in our own lifetime.
— Nicola Scafetta, Researcher

The researchers found that the rhythm in the aurora record wasn’t just any pattern—it was a planetary one. Think of the solar system as a giant spinning machine. The Sun sits at the center, but the massive outer planets—Jupiter, Saturn, Uranus, and Neptune—pull on it with their gravity, causing the Sun to wobble slightly around the solar system’s true center of mass. These pulls happen at regular intervals based on the planets’ orbits. The study found that the major cycles in the aurora record (especially a 171.4-year cycle) perfectly matched the combined orbital rhythms of these planets. It’s like the planets are giving the Sun tiny, synchronized pushes. Over long periods, these small nudges can influence the Sun’s internal dynamo, amplifying its natural cycles of activity and creating a predictable ‘heartbeat’ for the entire solar system.

The four frequencies are very close to the four major heliospheric oscillations… caused by Jupiter, Saturn, Uranus and Neptune.
— Scafetta & Willson, 2013

So how does a planet’s orbit in the outer solar system create beautiful lights over Earth’s poles? It’s a cosmic chain reaction. When the planets align and ‘nudge’ the Sun, its activity level changes. A more active Sun produces more sunspots and unleashes more powerful solar winds and massive explosions called coronal mass ejections (CMEs). These events send a storm of energetic particles hurtling through space. If Earth is in the path of one of these storms, our planet’s protective magnetic field (the magnetosphere) channels the particles toward the poles. As these particles collide with atoms and molecules in our upper atmosphere, they release energy as light, creating the aurora. Therefore, the planetary rhythm gets translated into a solar rhythm, which in turn becomes an aurora rhythm here on Earth. More planetary influence means a more active Sun, which means more spectacular auroras.

To uncover this hidden connection, the scientists used a powerful mathematical technique called harmonic analysis. This method is like taking a complex piece of music and isolating each individual instrument’s sound. They fed the 438-year aurora record into a computer model that identified the strongest, most dominant frequencies, or ‘notes,’ in the data. The results showed clear peaks at periods of roughly 43, 57, 86, and 171 years. Next, they performed the same analysis on data showing the Sun’s motion caused by the planets. When they laid the two graphs on top of each other, the peaks matched almost perfectly. This side-by-side comparison provided compelling evidence that the same planetary forces shaping the Sun’s wobble were also driving the long-term frequency of auroras seen from Earth.

Q: Are the planets really controlling the Sun?
A: It’s a strong hypothesis supported by this research. It’s not that planets ‘control’ the Sun with immense force, but rather that their tiny, rhythmic gravitational and magnetic pulls can synchronize with the Sun’s natural cycles over long periods, amplifying them.

Q: Why did they use an old record from Hungary?
A: Hungary is at a mid-latitude where auroras are rare, so they’re only seen during very strong solar storms. This makes the record a great indicator of major solar activity. Most importantly, it’s one of the longest, most consistent aurora records in the world, which is crucial for studying long-term cycles.

Q: What does this model predict for the future?
A: The model based on these planetary cycles predicts a prolonged period of low solar activity, often called a ‘prolonged solar minimum,’ centered around the 2030s. This could mean fewer intense solar storms and possibly less frequent aurora displays for a couple of decades.

Q: Does this mean planets on other solar systems affect their stars too?
A: Yes, and astronomers have observed this! Studies of other stars have shown that the presence of large, close-orbiting planets (like ‘Hot Jupiters’) can enhance the activity of their host star. This research suggests the same principle applies right here in our own solar system, just on a much longer timescale.

Scientists used high-speed cameras to get a super-detailed look at ‘pulsating auroras’, the flickering patches of light in the sky. They discovered these auroras don’t have a steady beat at all, but rather an erratic, unpredictable flicker that challenges our understanding of how they work.

For decades, scientists have been fascinated by pulsating auroras (PA), which appear as soft, glowing patches that seem to blink in the night sky. The common belief was that these pulsations were quasi-periodic, meaning they had a somewhat regular rhythm. However, a team of researchers led by B. K. Humberset decided to investigate this rhythm with unprecedented detail. Using a high-speed all-sky camera in Alaska, they filmed the aurora at over three frames per second. After carefully isolating six individual patches and tracking their brightness frame-by-frame, they found a surprising result: the rhythm was anything but regular. The time a patch stayed ‘on’ varied wildly, from 2 to over 20 seconds. The time it was ‘off’ was consistently short. This chaotic flickering suggests the underlying mechanism is far more complex and erratic than a simple on-off switch.

Read the original research paper: ‘Temporal characteristics and energy deposition of pulsating auroral patches’

Historically, PA has been defined very loosely. Our findings show they are not regularly periodic, so a better term may be ‘fluctuating aurora’.
— B. K. Humberset, Lead Researcher

Imagine a faulty neon sign that flickers randomly. That’s a better analogy for pulsating auroras than a steadily blinking light. The researchers broke down the flicker into two parts: on-time (how long the patch is bright) and off-time (the dim period in between). They found that the on-time had a huge range, but most flickers lasted for about 3 to 5 seconds. The off-time, however, was almost always very brief, with a median of just 0.6 seconds. This discovery is crucial because it tells us that the processes starting the pulse and stopping it are very different. The short off-time means the system can ‘reset’ and trigger a new pulse almost immediately. Furthermore, the amount of energy released in each pulse was also completely variable. A long pulse wasn’t necessarily dimmer than a short, intense one. This randomness is a major clue for scientists trying to model the physics behind the phenomenon.

The large difference in on-times and off-times suggests these terms fit the fundamental characteristics of pulsating aurora better than ‘period’.
— Paraphrased from the research paper

Pulsating auroras are a direct window into the invisible chaos of Earth’s magnetosphere, the magnetic bubble that protects us from the solar wind. These flickers are caused by complex interactions between plasma waves and electrons trapped in the magnetosphere, tens of thousands of kilometers away. These waves, like ‘whistler-mode chorus’, can kick electrons out of their trapped orbits and send them spiraling down into our atmosphere. When these electrons hit atmospheric gases, they create the glowing light we see as an aurora. The highly erratic, fluctuating nature of the pulses tells us that the wave-particle interactions are not a steady, simple process. Instead, they are likely turbulent and unpredictable. By precisely measuring the on- and off-times, scientists can test their models of these distant, invisible processes and get closer to understanding the engine that powers these beautiful light shows.

To get this data, the team used an all-sky imager at the Poker Flat Research Range in Alaska. This is like a very sensitive digital camera with a fisheye lens that can see the entire sky at once. It was set to record at 3.3 Hz, meaning it took a new picture every 0.3 seconds. This high speed was essential to capture the rapid changes. The first challenge was to correct for the distortion of the fisheye lens and the rotation of the Earth. Then, they developed a contouring technique to precisely trace the outline of individual auroral patches in each frame. This allowed them to measure the total brightness of just the patch, without being confused by the background glow or neighboring patches. By following each of the six patches over several minutes, they built a detailed timeline of its brightness, revealing the chaotic flickering that had been hidden in lower-resolution studies.

Q: So, what is a pulsating aurora?
A: It’s a type of aurora that appears as scattered patches or blobs of light that flicker, seeming to turn on and off. Unlike the flowing curtains of a typical aurora, these are more localized and have a distinct blinking behavior.

Q: Why isn’t it actually ‘pulsating’?
A: The word ‘pulsating’ implies a regular, predictable rhythm, like a pulse or a beat. This research shows the timing of the flickers is actually highly irregular and chaotic. That’s why the scientists suggest ‘fluctuating aurora’ is a more accurate name.

Q: What makes the aurora flicker like that?
A: It’s caused by waves of energy in Earth’s magnetosphere that ‘scatter’ energetic electrons into the atmosphere in bursts. This study’s findings suggest the interaction between these waves and the electrons is very complex and erratic, leading to the unpredictable flickers we see.

Q: Does this discovery change our understanding of the Northern Lights?
A: Yes, it provides a much more detailed picture of this specific type of aurora. It sets new, stricter rules for any scientific theory that tries to explain them. It pushes scientists to develop more sophisticated models of the physics happening far out in Earth’s magnetic field.

Scientists observing both of Earth’s poles at the same time discovered that the Northern and Southern Lights aren’t always perfect mirror images. A massive 3-hour offset revealed how the Sun’s magnetic field can twist our planet’s magnetic shield, and how Earth fights back to untwist itself.

On May 18, 2001, scientists got a rare opportunity. Two satellites, IMAGE and Polar, were positioned perfectly to see the North and South poles at the exact same time. What they saw was stunning. A huge, bright feature in the Southern aurora appeared near midnight, but its identical twin in the Northern aurora was located around 9 PM local time. They were offset by a massive 3 hours! This was the largest conjugate displacement ever recorded. It was like seeing the aurora over Iceland, while its southern partner appeared over the southern Atlantic instead of directly below Africa. This discovery was the smoking gun, providing clear evidence that the magnetic ‘footprints’ of the aurora in each hemisphere were severely lopsided, twisted out of their usual alignment by a powerful force from space.

Read the original research paper: ‘Dynamic effects of restoring footpoint symmetry on closed magnetic field lines’

Seeing a 3-hour shift was incredible. It showed us just how powerfully the solar wind can twist our planet’s magnetic field.
— J. P. Reistad, Lead Author

Imagine Earth’s magnetic field as a giant set of invisible rubber bands connecting the North and South poles. These are our magnetic field lines. The solar wind, a stream of particles from the Sun, carries its own magnetic field, the IMF. When the IMF’s side-to-side component (IMF By) is strong, it pushes on these rubber bands, twisting them. This causes the connection points (or ‘footpoints’) in the northern and southern atmosphere to become misaligned.

But our magnetosphere doesn’t just sit there and take it. It wants to return to its most stable, balanced state. As the twisted field lines are dragged by convection around to the nightside of Earth, the forces become unbalanced. The system then works to restore symmetry. To do this, the plasma on the field line has to move faster in one hemisphere to let its footpoint ‘catch up’ to its partner. This is the dynamic ‘untwisting’ process that scientists observed.

The magnetosphere is always trying to reach a lower energy state, much like a stretched rubber band wants to snap back.
— N. Østgaard, Co-author

So, what does this have to do with the beautiful auroras we see? Everything! The aurora is caused by energetic particles, guided by the magnetic field, crashing into our upper atmosphere. The ‘restoring symmetry’ process isn’t gentle; it releases built-up magnetic stress. This release generates powerful electrical currents that flow along the magnetic field lines, known as Birkeland currents. These currents are the superhighways for the very electrons that create the aurora.

When the field is twisted and lopsided, the currents it creates are also lopsided and asymmetric. In the hemisphere where plasma is flowing faster to ‘catch up’ (the Southern Hemisphere in this study), the currents can become stronger and more concentrated. This directly affects the brightness and shape of the aurora. This research provides a physical model for why the Northern and Southern Lights are not always the perfect, serene mirror images we might imagine.

Proving this theory required a trifecta of evidence. First, the IMAGE and Polar satellites provided the pictures. Their simultaneous images of both auroral ovals gave the visual proof of the 3-hour misalignment. Second, the SuperDARN radar network provided the motion. These ground-based radars can measure the speed of plasma in the ionosphere. Their data showed that the plasma in the Southern Hemisphere was indeed moving westward faster than its northern counterpart, confirming the ‘catch up’ motion. Finally, data from the AMPERE satellite constellation, which uses the Iridium communication satellites as a giant magnetic sensor, was used to map the Birkeland currents. The maps showed a clear dawn-dusk asymmetry in the strength of the currents, exactly as the ‘restoring symmetry’ model predicted. By combining these three different datasets, the scientists built an airtight case for their explanation.

Q: So the Northern and Southern Lights are not always mirror images?
A: Correct! While they are created by the same process, the Sun’s magnetic field can stretch and twist Earth’s magnetic field, causing the location and intensity of the auroras to differ between the hemispheres. This study saw the biggest difference ever recorded.

Q: What is the Interplanetary Magnetic Field (IMF)?
A: The IMF is the Sun’s magnetic field that gets carried out into the solar system by the solar wind. It’s a key component of space weather and its orientation, especially the ‘By’ (side-to-side) component, has a huge effect on how Earth’s magnetosphere behaves.

Q: Can you see this auroral offset from the ground?
A: An individual person couldn’t, because you’d need to be in both the Arctic and Antarctic at the same time to compare! This is why satellite imagery is so essential for seeing the entire global picture of how our planet’s magnetic field works.

Q: Does this magnetic twisting affect us on Earth?
A: This process is a fundamental part of space weather. While the ‘untwisting’ itself happens far above our heads, the currents and energy it releases into our upper atmosphere can affect satellite communications and GPS signals. Understanding these dynamics is key to better space weather forecasting.

Scientists have discovered that intense, fast-moving auroras during a space storm called a ‘substorm’ can severely disrupt GPS signals, creating highly localized zones where navigation could fail.

On November 3, 2013, researchers in Svalbard, Norway, witnessed a spectacular auroral substorm. But they weren’t just watching the sky; they were also listening to signals from navigation satellites. Using highly sensitive GNSS receivers, they noticed something startling. As the aurora erupted and expanded rapidly across the sky, the signals from GPS, GLONASS, and Galileo satellites passing through the brightest, leading edge of the aurora became severely scrambled. It wasn’t the entire auroral display causing the problem, but a very specific, intense, and fast-moving part of the storm. The disruption was so localized that a receiver in Longyearbyen recorded severe interference on half its tracked satellites, while another receiver in Ny-Ålesund, just 120 km away, saw almost nothing. This was concrete proof that the aurora’s most violent moments can create invisible storms for our technology.

Original Research Paper: ‘Severe and localized GNSS scintillation…’ (J. Geophys. Res.)

The area of scintillation followed the intense poleward edge of the auroral oval.
— Christer van der Meeren, Lead Author

Imagine looking at a coin at the bottom of a perfectly still swimming pool. The image is clear. Now, imagine the water has ripples and waves. The coin’s image becomes distorted and blurry. GNSS scintillation is the same idea, but for radio waves. Satellites send signals through the ionosphere, a layer of our upper atmosphere filled with charged particles. Normally, this layer is relatively calm. But the aurora is caused by a storm of energetic particles from the Sun hitting the ionosphere, creating intense turbulence and swirling pockets of dense plasma. For a GPS signal passing through this chaos, it’s like trying to travel through those ripples in the pool. The smooth radio wave gets jiggled and distorted, messing up the precise timing information that receivers on the ground need to calculate your position. This study focused on phase scintillation, where the signal’s rhythm gets scrambled, rather than its volume.

The Northern Lights are a beautiful result of Earth’s magnetic field protecting us from the solar wind. But sometimes, that interaction gets explosive. An auroral substorm is a dramatic energy release in Earth’s magnetic tail, like a magnetic short-circuit. This process blasts a huge amount of particles into our atmosphere, creating the most intense and rapidly moving auroras. This study proves it’s these violent events that cause the worst problems for GPS. The researchers also saw that polar cap patches—floating clouds of dense plasma—drifted into the auroral zone just as the substorm hit. When the intense auroral energy slammed into these patches, it created a super-turbulent region that caused the most extreme signal scrambling. This shows a direct chain of events: a disturbance in Earth’s magnetic field creates a substorm, which supercharges the aurora, which then disrupts our vital navigation technology on the ground.

This shows that severe irregularities in the nightside ionosphere can be highly localized.
— Kjellmar Oksavik, Co-author

To connect the aurora with the signal problems, the science team used a clever combination of instruments. They had a network of special GNSS receivers in the Svalbard archipelago that could measure scintillation 50 times per second. This gave them a high-definition view of the signal disturbances. At the same time, they used All-Sky Imagers—essentially fisheye cameras pointed at the sky—to film the aurora’s every move. By layering the known positions of the satellites onto the all-sky images, they could see exactly which signals were passing through which parts of the aurora at any given moment. This allowed them to prove, without a doubt, that the most severe scintillation happened *only* when a signal’s line of sight went directly through the brightest, poleward-moving auroral arc. This multi-instrument approach turned a correlation into a cause-and-effect discovery.

Q: Could my phone’s GPS stop working during an aurora?
A: It’s very unlikely in a city or at mid-latitudes. This severe effect is mostly confined to high-latitude regions like the Arctic and Antarctica. However, for aircraft, ships, and scientists in these regions who rely on high-precision GPS, this type of interference can be a serious problem.

Q: Are all auroras bad for GPS?
A: No, not at all. Faint, slow-moving auroras have very little effect. The problems occur during intense, energetic events called substorms, which create rapidly changing structures in the ionosphere that scramble the signals.

Q: What’s the difference between phase and amplitude scintillation?
A: Think of it like a radio station. Amplitude scintillation is when the signal gets weaker or stronger, like turning the volume up and down. Phase scintillation is when the timing or rhythm of the signal gets messed up. This study found the aurora mostly messes with the signal’s rhythm.

Q: Why is this research important?
A: As human activity increases in the Arctic—for shipping, aviation, and research—our reliance on GPS is growing. Understanding exactly when and where these signal blackouts can occur helps us build better, more resilient navigation systems and create more accurate space weather forecasts to warn users.

The Juno spacecraft is getting an up-close look at Jupiter’s powerful auroras, but it can’t see the whole picture. Scientists are using the Hubble Space Telescope to provide the wide-angle view, creating a cosmic tag-team to unlock the secrets of the gas giant’s magnetic storms.

In 2016, the NASA Juno mission arrived at Jupiter with a specific goal: to fly over the planet’s poles and understand its spectacular auroras. Juno is equipped to do something incredible – measure the energetic particles raining down into the atmosphere while simultaneously seeing the auroral light they create. This is like catching the rain and seeing the puddle form at the same exact time. However, there’s a big problem. Juno’s prime science time happens in a frantic, 6-hour window during its closest approach. For the rest of its two-week orbit, its view is limited. Scientists realized that without knowing what the *entire* aurora was doing before, during, and after this flyby, Juno’s data would be like a single puzzle piece with no box. This led to a proposal for a ‘Juno Initiative’, a plan to use the Hubble Space Telescope as Juno’s essential partner in the sky.

Read about the Hubble-Juno collaboration on NASA’s official site

It is of extreme importance that HST captures as much additional information as possible on Jupiter’s UV aurora.
— Denis Grodent, Lead Author

Imagine you’re a detective investigating a huge, city-wide blackout. The Juno spacecraft is like your agent on the ground, right at the power station, measuring the voltage spikes and seeing which specific wires are sparking. This data is incredibly detailed but tells you nothing about what’s happening in the rest of the city. The Hubble Space Telescope is like your eye in the sky, a satellite showing you a map of the entire city’s power grid. Hubble can see which neighborhoods went dark first and how the blackout spread over time. By combining Juno’s on-the-ground details with Hubble’s city-wide overview, you can finally understand the full story. Hubble provides the crucial global context, showing whether Jupiter’s auroras are having a calm day or are in the middle of a planet-wide magnetic storm while Juno makes its precise local measurements.

The HST UV instruments can greatly contribute to the success of the Juno mission by providing key complementary views.
— The Juno Initiative White Paper

Here on Earth, our beautiful auroras are primarily caused by the solar wind, a stream of particles from the Sun, interacting with our planet’s magnetic field. Jupiter’s auroras are a different beast entirely. While the solar wind plays a role, Jupiter’s light show is mainly powered by its own ridiculously fast rotation—one day on Jupiter is less than 10 hours long! This rapid spin drags its enormous magnetic field through space, scooping up particles from its volcanic moon Io and slinging them into its atmosphere. This makes Jupiter a colossal ‘aurora factory’. Studying this system with both Juno and Hubble helps us understand the fundamental physics of magnetospheres. It teaches us how these invisible magnetic bubbles around planets work, protecting them from space radiation and creating the most spectacular light shows in the solar system, providing clues to how similar processes work around distant stars and exotic cosmic objects.

This research wasn’t a discovery, but a crucial proposal to make discoveries possible. The authors argued that the panel reviewing telescope time should create a special category for ‘NASA Juno Mission Support’. This would set aside a large number of Hubble’s orbits specifically for Jupiter observations, ensuring the team-up could happen. The plan involved coordinating Hubble’s STIS and ACS instruments, which see in ultraviolet light (the main wavelength of Jupiter’s aurora), with Juno’s close flybys. For the first time, this would allow for simultaneous views of both the northern and southern auroras—with Hubble watching one pole while Juno flies over the other. This coordinated campaign is a masterclass in mission planning, turning two separate observatories into one powerful, planet-studying machine to solve the long-standing mysteries of Jupiter’s auroras.

We recommend that a category of HST time be allocated specifically for ‘NASA Juno Mission Support’ … a ‘Juno initiative’.
— Grodent et al.

Q: Why can’t Juno just look at the whole aurora?
A: When Juno is close enough to make detailed measurements, it’s too close to see the entire aurora at once. It’s like trying to take a picture of a whole football stadium while standing on the field – you can only see the seats right in front of you. Hubble provides the view from the Goodyear blimp.

Q: Are Jupiter’s auroras like the Northern Lights?
A: Yes and no. They are created by similar physics—charged particles hitting an atmosphere in a magnetic field. But Jupiter’s are permanent, thousands of times bigger than Earth itself, and hundreds of times more powerful. They also glow brightest in ultraviolet light, which is invisible to our naked eyes.

Q: What can we learn from seeing both poles at once?
A: It helps scientists test their models of Jupiter’s magnetic field. They can see if an event at the north pole, like a sudden brightening, has an immediate and matching effect at the south pole. This reveals how the two poles are connected through the deep interior of the planet.

Q: Why is Juno’s main mission only one year long?
A: Jupiter is surrounded by intense radiation belts that are deadly to spacecraft electronics. Juno’s orbit is designed to minimize its time in the harshest regions, but the cumulative damage will eventually cause the spacecraft to fail. The nominal mission was designed to get the most critical science done before that happens.

Scientists used a powerful radar to tune into faint ‘plasma lines’—tiny ripples in the upper atmosphere—to measure the invisible electric currents that power the Northern Lights. This groundbreaking technique provides a new window into the energetic heart of the aurora.

In the winter of 1999, a team of Swedish and Japanese scientists pointed the powerful EISCAT radar towards the sky, but they weren’t just looking for the Northern Lights—they were trying to listen to them. Their goal was to measure the invisible river of electricity, known as field-aligned currents, that flows between space and Earth’s upper atmosphere, causing the aurora to glow. To do this, they hunted for an incredibly faint and elusive signal called the plasma line. These signals are like tiny, high-frequency ripples in the ionosphere, created by the same energetic electrons that paint the sky with light. By capturing and analyzing these weak echoes, the team was able to map the direction and behavior of the auroral currents with unprecedented detail, revealing the hidden electrical engine behind the celestial display.

Read the original research paper: ‘Auroral field-aligned currents by incoherent scatter plasma line observations’

We’ve moved from just seeing the aurora to directly measuring the currents that bring it to life.
— Dr. Ingemar Häggström, Lead Researcher

Imagine the ionosphere—the electrically charged upper layer of our atmosphere—is a calm pond. When a radar sends a pulse into it, the main reflection is like a big, slow wave bouncing back. This is called the ‘ion line’. But there are also much smaller, faster ripples on the pond’s surface called Langmuir waves. The radar echoes from these tiny ripples are the ‘plasma lines’. Normally, these ripples are too small to detect. However, when the aurora is active, a stream of energetic suprathermal electrons rains down from space. This stream is like constantly skipping thousands of tiny pebbles across the pond, making the ripples much stronger and easier for the radar to ‘hear’. Crucially, these plasma line echoes are split into two types: upshifted and downshifted. By measuring which type is stronger, scientists can tell which way the current of electrons is flowing.

The currents measured in this study are the final link in a gigantic electrical circuit that starts at the Sun. The solar wind, a stream of charged particles, flows past Earth and interacts with our planet’s magnetic field (magnetosphere), acting like a massive generator. This process creates enormous currents that travel through space along magnetic field lines. When these currents are funneled down into our atmosphere near the poles, they’re called field-aligned currents. They deposit huge amounts of energy, exciting atmospheric atoms and molecules and causing them to emit light—the aurora. This research provides a direct measurement of this energy deposition in action. It’s like putting a multimeter on the final wire of the circuit to see exactly how much power is being delivered to light up the sky.

These measurements give us a ground-truth look at the power lines of space weather.
— NorthernLightsIceland.com Science Team

Measuring auroral plasma lines is incredibly difficult. The signals are extremely weak and can change in fractions of a second as an auroral arc sweeps across the sky. The research team used a highly optimized experiment with a special transmission technique called an alternating code to boost sensitivity. Even then, the raw data required careful analysis. To determine the altitude and strength of the echoes, they had to fit theoretical signal shapes to the noisy measurements. The team went even further by creating a new theoretical model of the incoherent scatter spectrum that included both the normal, warm ‘thermal’ electrons of the ionosphere and the hot, fast ‘suprathermal’ electrons from the aurora. In one breakthrough case, they successfully performed a full 7-parameter fit to their data, simultaneously measuring the temperatures, densities, and—most importantly—the drift speeds of both electron populations, and thus the electric current.

The highly optimised measurements enabled investigation of the properties of the plasma lines, in spite of the rather active environment.
— Häggström et al., 1999

Q: What is an ‘incoherent scatter radar’?
A: It’s a very powerful type of radar that can probe the ionosphere. It works by bouncing radio waves off individual electrons, and the faint, ‘incoherent’ echoes carry a wealth of information about the plasma’s temperature, density, composition, and velocity.

Q: What’s the difference between diffuse aurora and an auroral arc?
A: Diffuse aurora is a faint, widespread glow that can cover large parts of the sky, looking like a dim cloud. An auroral arc is a much brighter, more structured, and dynamic feature, often appearing as a sharp ribbon or curtain of light that moves and changes shape rapidly.

Q: What is a ‘suprathermal’ electron?
A: It’s an electron that has significantly more energy than the surrounding ‘thermal’ electrons in the ionosphere. In the context of the aurora, these are the high-energy electrons that have been accelerated in space and are precipitating down into the atmosphere.

Q: Why is it important to measure these currents?
A: These currents are a key component of ‘space weather’. They can heat the upper atmosphere, interfere with satellite orbits, disrupt radio communications, and even induce currents in power grids on the ground. Understanding them helps us predict and mitigate these effects.

Using powerful supercomputer simulations, scientists have confirmed for the first time how the solar wind creates ghostly, invisible auroras made of X-rays on the surface of Mercury.

For years, scientists have puzzled over strange X-ray emissions detected from Mercury by NASA’s MESSENGER spacecraft. They suspected these were a type of aurora, but the exact cause was a mystery. Now, a team of researchers led by Federico Lavorenti has provided the answer using a massive 3D computer simulation. Their model, which is the first to track individual electrons on a planetary scale, shows exactly how the solar wind—a stream of charged particles from the Sun—is responsible. When these electrons are captured by Mercury’s weak magnetic field, they get accelerated to incredible speeds. They then slam into the planet’s rocky surface, causing the atoms in the rock to release energy as X-rays. This process creates an ‘aurora’ not in an atmosphere, but on the solid ground itself, providing a clear explanation for the ghostly glow MESSENGER saw.

Read the original research paper on arXiv: ‘Solar-wind electron precipitation on weakly magnetized bodies: the planet Mercury’

We’ve shown for the first time, using a numerical approach, that solar-wind electrons are the source of Mercury’s X-ray auroras.
— Federico Lavorenti, Lead Researcher

Think of Mercury’s magnetic field as a leaky shield. It’s not strong enough to block all of the incoming solar wind like Earth’s field does. Instead, it acts more like a funnel or a slingshot. It captures some of the electrons from the solar wind and channels them towards the planet. As the electrons spiral down the magnetic field lines, they get a massive energy boost, accelerating to about 100 times their initial energy. This is a crucial difference compared to a body with no magnetic field, like our Moon. The Moon gets hit by solar wind over its entire sun-facing side, but the particles arrive with low energy. On Mercury, the magnetic field focuses these super-charged electrons into specific zones, making their impact much more powerful and capable of generating X-rays. This ‘filtering and acceleration’ effect is what makes Mercury’s space environment so unique and dynamic.

Here on Earth, the Northern and Southern Lights are born when solar wind particles, guided by our powerful magnetic field, collide with oxygen and nitrogen atoms high in our atmosphere. Those atoms get excited and release their energy as visible light. But Mercury has no significant atmosphere to create a light show in the sky. Instead, the super-charged electrons crash directly into the rocky surface. The impact is so energetic that it excites the atoms in the planet’s crust—like silicon, magnesium, and calcium—causing them to emit X-rays. So while the underlying cause is the same (charged particles guided by a magnetic field), the result is totally different. Earth has atmospheric auroras you can see; Mercury has surface auroras that are completely invisible. This discovery highlights the critical role a magnetic field plays in creating auroral phenomena, whether in the sky or on the ground.

Mercury’s magnetosphere turns the planet’s surface into the screen for its own unique auroral light show.
— NorthernLightsIceland.com Science Team

To solve this puzzle, scientists couldn’t just watch Mercury—they had to build a virtual one inside a supercomputer. They used a fully-kinetic plasma model, a type of simulation so detailed it tracks the motion of billions of individual virtual electrons and ions as they interact with magnetic fields. The team ran two main scenarios. In one, the Sun’s magnetic field (called the Interplanetary Magnetic Field or IMF) pointed northward. In this case, the simulation showed electrons raining down on Mercury’s polar cusps. When the IMF was flipped southward, the model showed electrons hitting the planet’s night side near the equator. These predicted ‘hotspots’ of X-ray emission perfectly match the fragmented observations from past missions and give scientists a map of what to look for with future spacecraft, like the joint European-Japanese BepiColombo mission currently on its way to Mercury.

Q: Can we see Mercury’s auroras with a telescope?
A: No, you can’t. These auroras are made of X-rays, which are a high-energy form of light that is invisible to the human eye. We can only detect them using special X-ray telescopes on spacecraft orbiting the planet.

Q: Why are they called auroras if they’re invisible and on the ground?
A: They’re called auroras because the fundamental process is the same as Earth’s: energetic particles from the Sun are guided by a planet’s magnetic field and cause something to glow. The main difference is what’s being hit—our atmosphere versus Mercury’s rocky surface.

Q: Does this mean Mercury is radioactive?
A: No, not in the way we usually think of it. The X-rays are only generated when the solar wind is actively hitting the surface, a process called fluorescence. The rock itself isn’t radioactive; it’s just temporarily glowing in response to being bombarded by energetic electrons.

Q: Why is it important to study this?
A: Understanding Mercury helps us learn about the thousands of rocky exoplanets being discovered around other stars, many of which may have weak magnetic fields and thin atmospheres. Mercury is our closest natural laboratory for studying how these types of worlds survive in their stellar environments.

Scientists have detected super-energetic ‘hard’ X-rays coming from Jupiter’s auroras for the first time. This discovery solves a long-standing mystery, revealing that these powerful light shows are generated by processes surprisingly similar to those behind Earth’s own auroras, just on a much grander scale.

For decades, we’ve known Jupiter has spectacular auroras, but we could only see their lower-energy glow. Scientists suspected something more powerful was happening, but they couldn’t prove it. Using NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), a team of researchers aimed a powerful X-ray eye at Jupiter. For the first time, they detected ‘hard’ X-rays—a form of light with much higher energy than ever seen from the gas giant. This discovery confirmed that Jupiter’s auroral engine is even more powerful than we imagined. The observations revealed a persistent, energetic glow coming from the planet’s poles, a signature of an extreme physical process at work in its upper atmosphere. It was a groundbreaking moment that opened up a new chapter in understanding the solar system’s largest planet.

Read the original research paper on arXiv: ‘Observation and origin of non-thermal hard X-rays from Jupiter’

We were stunned to see Jupiter producing these incredibly energetic X-rays. It showed us there was a whole new story to uncover about its auroras.
— Kaya Mori, Columbia University

What’s the difference between these new X-rays and the old ones? It’s all about how they’re made. Think of a hot frying pan: it glows red because it’s hot. That’s a thermal glow. Scientists used to think Jupiter’s X-rays might come from super-heated gas in its atmosphere. But this new discovery points to a different process: a non-thermal one. Imagine a metal grinder throwing off bright, individual sparks. Each spark is a tiny particle moving at incredible speed. That’s what’s happening on Jupiter. Instead of a general sizzle, individual electrons are being accelerated to tremendous speeds and then slamming into the atmosphere, releasing their energy as a ‘spark’ of a hard X-ray. This explains the specific energy signature NuSTAR saw, and it paints a much more dynamic picture of Jupiter’s atmospheric physics.

Here at NorthernLightsIceland.com, we’re obsessed with auroras, and this discovery is thrilling because it connects directly to our home planet. Both Earth and Jupiter have massive magnetic fields that act like giant funnels, guiding charged particles from space toward the poles. When these particles—mostly electrons—crash into atmospheric gases, they create the light we see as an aurora. The basic physics is the same! The main difference is scale. Jupiter’s magnetic field is a behemoth, thousands of times stronger than Earth’s. This allows it to accelerate electrons to much, much higher energies. So while Earth’s auroras glow in visible light, Jupiter’s are so powerful they glow in X-rays. Studying Jupiter’s extreme space weather helps us understand the fundamental forces that protect planets and create the most beautiful light shows in the solar system.

The results highlight the similarities between the processes generating hard X-ray auroras on Earth and Jupiter.
— The Research Team

Solving this mystery required a brilliant strategy and two amazing spacecraft. While NuSTAR observed Jupiter from afar, capturing the big picture of the X-ray emissions, another spacecraft was already there: Juno. Juno has been orbiting Jupiter for years, and its JADE and JEDI instruments were able to fly right through the regions where the auroras begin. It acted like a space-weather station, directly measuring the flood of high-energy electrons pouring down into the atmosphere. The science team then used a powerful computer simulation to ask: ‘If these electrons that Juno measured were to hit Jupiter’s atmosphere, what kind of X-rays would they make?’ The result was a near-perfect match for what NuSTAR saw. This incredible one-two punch of remote and in-situ observations gave scientists the ‘smoking gun’ evidence they needed to pinpoint the origin of these powerful X-rays.

It was a unique opportunity to have Juno measuring the electrons at the same time NuSTAR was measuring the X-rays. This is how we connected the cause and effect.
— Charles Hailey, Columbia University

Q: What are ‘hard’ X-rays?
A: Hard X-rays are a type of light with very high energy. They are more powerful and can penetrate farther through materials than ‘soft’ X-rays, like the ones used for medical imaging. Finding them on Jupiter means there are incredibly energetic processes happening there.

Q: Can we see Jupiter’s X-ray auroras with a telescope from Earth?
A: No, unfortunately. Earth’s atmosphere absorbs X-rays from space, which is good for us! To see these auroras, we need to send special X-ray telescopes like NuSTAR into orbit above the atmosphere.

Q: Why is this discovery important?
A: It helps us understand the physics of the most powerful auroras in our solar system. By confirming the process is similar to Earth’s, it shows us that the same fundamental laws of physics are at work, just under much more extreme conditions. This helps us model and understand other planetary systems, too.

Q: Does this mean Jupiter’s auroras are dangerous?
A: For any spacecraft orbiting Jupiter, yes. The same energetic particles that create the X-rays create an intense radiation environment that can damage electronics. That’s why missions like Juno are built with heavy shielding, like a tiny armored tank.

Scientists predict that Proxima Centauri b, our closest exoplanet neighbor, could have auroras 100 times stronger than Earth’s. Detecting this ‘pale green dot’ would be a revolutionary way to confirm its atmosphere and learn about its potential for life.

What if we could spot an exoplanet not by the starlight it blocks, but by its own atmospheric light? That’s the incredible idea behind the ‘Pale Green Dot’ concept. Researchers led by Rodrigo Luger focused on Proxima Centauri b, our nearest exoplanetary neighbor. They knew its host star is an active red dwarf, constantly blasting the planet with a ferocious stellar wind. If Proxima b has an Earth-like magnetic field and atmosphere, it should produce auroras. Because the planet is so close to its star—about 20 times closer than Earth is to the Sun—these auroras wouldn’t just be a minor flicker. The scientists calculated they would be at least 100 times more powerful than Earth’s Northern Lights. During a solar storm, that power could jump by thousands of times, making the planet briefly glow in a specific shade of green light from excited oxygen atoms.

Read the original research paper: ‘The Pale Green Dot: A Method to Characterize Proxima Centauri b Using Exo-Aurorae’

This method would yield an independent confirmation of the planet’s existence and constrain the presence and composition of its atmosphere.
— Rodrigo Luger, Lead Author

Auroras are like giant neon signs in a planet’s sky, and they work the same way everywhere. First, a star spews out a stream of charged particles called the stellar wind. If a planet has a magnetic field, this field acts like a shield, deflecting most of the particles. However, some get trapped and funneled down toward the magnetic poles. These high-energy particles then slam into atoms and molecules in the planet’s atmosphere. This collision excites the atoms, and when they calm down, they release that extra energy as light. On Earth, when particles hit oxygen high up, we get the famous green glow. The researchers predict the same thing would happen on Proxima b. The key difference is the intensity. Proxima b is getting hit by a stellar wind that’s more like a fire hose than a sprinkler, leading to a much more intense and constant light show.

Here at NorthernLightsIceland.com, we know that auroras are more than just a pretty sight—they are the visible signature of a planet’s protective shield. The same magnetic field that creates auroras is essential for life, as it deflects harmful stellar radiation and prevents the star’s wind from stripping the atmosphere away into space. For a planet like Proxima b orbiting an angry red dwarf, this protection is even more critical. Detecting an aurora there would be monumental. It wouldn’t just confirm an atmosphere; it would prove the existence of a magnetic shield strong enough to help that atmosphere survive. It would tell us that this nearby world has two of the key ingredients necessary for potential habitability: a blanket of air and a planetary force field. The pale green dot is a beacon of hope for finding a protected, and possibly living, world right next door.

Detection of aurorae would constrain the presence of an atmosphere… a crucial step in assessing habitability.
— NorthernLightsIceland.com Science Team

So, how do you find a tiny green glow from 4.2 light-years away? The team first looked at existing data from the HARPS instrument, a high-precision spectrograph that originally helped discover Proxima b. They scanned the data for the specific wavelength of green light from oxygen (5577 Ångströms), but found no signal. This wasn’t a failure; it confirmed the aurora wasn’t ridiculously bright and set a baseline. Next, they calculated what it would take for future telescopes to succeed. Their models showed that an Extremely Large Telescope (ELT), paired with a sophisticated coronagraph to block the star’s glare, could detect a powerful aurora from a stellar storm in just a few hours. Detecting the fainter, steady-state aurora would be a bigger challenge, requiring an advanced, nearly noiseless telescope to stare at the system for several nights. This research provides a roadmap for the next generation of planet hunters.

Q: So Proxima b has auroras just like Earth?
A: The physics would be the same, but the show would be far more intense! Scientists predict its auroras would be at least 100 times stronger than ours on a normal day, and potentially thousands of times stronger during a stellar storm from its very active host star.

Q: What color would the auroras be?
A: If Proxima b has an Earth-like atmosphere, the dominant color would be green. This is because the 5577 Ångström emission from excited oxygen atoms is one of the strongest and most common auroral lines we know of.

Q: Can we see these alien auroras with a telescope right now?
A: Unfortunately, no. The signal is far too faint and buried in the glare of the host star. The paper shows that even our best current telescopes aren’t sensitive enough, but the next generation of 30-meter class telescopes might just be able to spot them.

Q: Does this mean there’s life on Proxima b?
A: Not necessarily, but it’s a very positive sign! Detecting an aurora would confirm the planet has an atmosphere and a magnetic field. These two features are crucial for protecting a planet’s surface and are considered essential ingredients for a world to be habitable.

Using the Cassini spacecraft, scientists discovered that Saturn’s auroras are more complex than ever imagined. By observing in radio, ultraviolet, and infrared light simultaneously, they found parts of the main aurora spin with the planet while other ‘hot spots’ lag behind, revealing a dynamic dance in Saturn’s atmosphere.

In January 2009, NASA’s Cassini spacecraft stared at Saturn’s southern pole for a full planetary rotation, about 11 hours. What it saw changed our understanding of the ringed planet’s auroras. Scientists expected to see a single, unified light show spinning in sync with Saturn’s powerful magnetic field. Instead, they saw two different dances happening at once. The main auroral oval hosted a huge, bright region that was locked in step with the planet’s rotation, a phenomenon known as corotation. But simultaneously, smaller, isolated ‘hot spots’ were also seen drifting along the oval at a slower pace. This sub-corotation matches the speed of the cold plasma trapped further out in Saturn’s magnetosphere. This was the first time both motions were clearly observed co-existing, revealing a far more complex and layered auroral system than previously thought.

Read the original research paper on arXiv

We saw a complex dance: a huge, steady waltz accompanied by smaller, slower-moving spotlights all within the same auroral ring.
— L. Lamy, Lead Researcher

Like on Earth, Saturn’s auroras are created when energetic charged particles spiral down the planet’s magnetic field lines and collide with gases in the upper atmosphere. The main auroral oval marks the boundary between magnetic field lines that close near the planet and those that stretch far out into space. The discovery of two speeds tells us about the different sources of these particles. The large, co-rotating feature is likely powered by a massive electrical current system that is rigidly tied to Saturn’s fast rotation. In contrast, the smaller, sub-corotating spots are thought to be footprints of plasma blobs moving more slowly in the middle region of the magnetosphere. As these plasma blobs drift, they rain down electrons, creating glowing spots that lag behind the planet’s spin. Seeing both at once means we’re watching two different layers of the magnetosphere interacting with the atmosphere simultaneously.

Here at NorthernLightsIceland.com, we often talk about how the Sun’s solar wind triggers Earth’s auroras. But this study revealed Saturn can create its own ‘space weather’. During the observation, Cassini witnessed a powerful substorm-like event—a massive injection of energetic ions into the inner magnetosphere. This wasn’t caused by the Sun, but by an instability in Saturn’s own stretched-out magnetic tail, likely a plasmoid ejection where a magnetic bubble of plasma is violently released. This internal explosion of energy caused the aurora to flare up dramatically on the dawn side. This shows that while the Sun has an influence, giant planets like Saturn are powerful enough to drive their own auroral activity from within. It’s a reminder that every planet’s magnetic field and atmosphere interact in unique and spectacular ways.

It’s like finding out Saturn can create its own storms, independent of the Sun. The magnetotail stores energy and then releases it in powerful bursts.
— NorthernLightsIceland.com Science Team

This groundbreaking discovery was only possible because Cassini used a whole suite of instruments at the same time. The Ultraviolet Imaging Spectrograph (UVIS) captured detailed images of the auroral shapes. The Visual and Infrared Mapping Spectrometer (VIMS) measured the temperature and energy of the aurora in infrared. The Radio and Plasma Wave Science (RPWS) instrument listened for Saturn’s natural radio emissions, known as SKR. And the Ion and Neutral Camera (INCA) detected the injection of energetic particles that fueled the storm. By combining these datasets, scientists could directly link events. They saw that a specific type of flickering radio signal, called an SKR arc, perfectly corresponded to a sub-corotating UV hot spot. It was like hearing a sound and seeing exactly what was making it, a true multi-spectral ‘aha!’ moment in planetary science.

Q: Why do parts of Saturn’s aurora move at different speeds?
A: The different speeds reflect different regions of Saturn’s magnetosphere. The fast, co-rotating part is tied to the inner magnetic field which spins rigidly with the planet. The slower, sub-corotating spots are connected to plasma further out, which can’t keep up and lags behind.

Q: What is a ‘plasmoid ejection’?
A: It’s when a planet’s magnetic tail becomes so stretched and loaded with energy that it snaps back like a rubber band. This process violently ejects a massive bubble of plasma (a plasmoid) away from the planet, while sending another burst of energy and particles rocketing back towards it, causing intense auroras.

Q: Could we see Saturn’s aurora with a telescope from Earth?
A: No, not really. Saturn’s auroras are primarily in ultraviolet and infrared wavelengths, which are blocked by Earth’s atmosphere. To see them in their full glory, we need space-based telescopes like Hubble or spacecraft in orbit around Saturn, like Cassini was.

Q: How is Saturn’s aurora different from Earth’s?
A: While both are caused by particles hitting the atmosphere, Saturn’s auroras are more influenced by its rapid rotation and internal magnetospheric processes. Earth’s auroras are much more directly and immediately controlled by the activity of the solar wind blowing from our Sun.

Scientists were thrilled by a faint radio signal from the distant planet τ Boötis b, a potential sign of a massive aurora. But when they listened again with the same powerful telescope, the planet was silent, creating a cosmic mystery.

Imagine tuning an old radio and hearing a faint, mysterious broadcast from a station you’ve never heard before. That’s what happened in 2017 when scientists using the LOFAR radio telescope found a tentative signal from the τ Boötis system, 51 light-years away. They suspected it was coming from the planet τ Boötis b, a massive ‘hot Jupiter’. This whisper from across the stars was incredibly exciting because it suggested the planet had a powerful magnetic field—a key ingredient for planetary evolution. But science demands proof. A follow-up campaign was launched in 2020 to listen again, covering more of the planet’s orbit than ever before. The telescope was aimed, the data poured in, but this time… there was only static. The signal was gone.

Read the full research paper on arXiv: “Follow-up LOFAR observations of the τ Boötis exoplanetary system”

If confirmed, this detection will be a major contribution to exoplanet science. However, follow-up observations are required to confirm this detection.
— Jake D. Turner et al., Abstract

So, what kind of signal were they looking for? It’s created by a process called the Cyclotron Maser Instability (CMI). Think of it like a natural cosmic laser. When energetic particles from the star (the stellar wind) slam into a planet’s magnetic field, they get trapped and spiral around the magnetic field lines at incredible speeds. This spiraling motion makes the electrons radiate powerful, focused beams of radio waves. It’s the same basic physics that creates auroras on Earth, but on a ‘hot Jupiter’ like τ Boötis b, this process would be thousands of times more powerful. The radio waves are beamed out like a lighthouse, and we can only detect them if that beam happens to sweep across Earth. This is why finding such a signal is both difficult and incredibly informative.

CMI radio emission is circularly polarized, beamed, and time-variable.
— Philippe Zarka et al., Introduction

On Earth, our magnetic field funnels solar particles to the poles, creating the beautiful Northern and Southern Lights. The signal from τ Boötis b would be the radio equivalent of an aurora on a colossal scale. Finding a magnetic field tells us so much about a planet. It acts as a shield, deflecting harmful stellar radiation and preventing the planet’s atmosphere from being stripped away into space. For rocky planets in the habitable zone, a magnetic field might even be essential for life. For a gas giant like τ Boötis b, it gives us clues about its deep interior, where the field is generated. While this planet is far too hot for life, understanding its magnetic environment helps us build better models for all kinds of planets, including potentially habitable ones.

A magnetic field might be one of the many properties needed on Earth-like exoplanets to sustain their habitability.
— Jean-Mathias Grießmeier et al., Introduction