phenomenon

aurora

A natural light display in the sky caused by charged particles interacting with a planet's magnetic field.
19 related articles

Description

An aurora is a natural light display in the sky, typically observed in high-latitude regions, caused by the interaction of charged particles from the solar wind with a planet's magnetic field and upper atmosphere. On Earth, auroras appear as shimmering curtains of green, red, and purple light near the polar regions. They are a visible manifestation of the complex coupling between the Sun and a planet's magnetosphere.

History

The term 'aurora borealis' was coined by Galileo Galilei in 1619, but the physical mechanism was only understood in the 20th century with the advent of space physics. Kristian Birkeland's experiments in the early 1900s first suggested the connection to charged particles.

How it works

The solar wind, a stream of charged particles, carries the Sun's magnetic field. When it reaches Earth, it compresses the magnetosphere on the day side and stretches it into a long tail on the night side. Some particles get trapped in the magnetosphere and are accelerated along magnetic field lines toward the poles. There, they collide with oxygen and nitrogen atoms in the upper atmosphere, exciting them. When these atoms relax back to their ground state, they emit photons of specific wavelengths, creating the characteristic colors: green and red from oxygen, blue and purple from nitrogen.

In practice

Auroras are studied to understand space weather, which can disrupt satellite communications, GPS, and power grids. They also occur on other planets, like Jupiter and Saturn, providing insights into their magnetic fields.

Fun fact

Auroras on Jupiter are not only in the ultraviolet and visible spectrum but also emit X-rays, a phenomenon that has puzzled scientists since its discovery in 1979.

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Related articles · 19

Stellar2026-08-302 minarXiv:2608.29649
Stellar2026-08-253 minarXiv:2608.24752
The Sun's Magnetic Pulse, Heard by Earth
The Sun breathes, and that breath has a magnetic rhythm. Every 27 days, the visible surface of the star makes a full rotation, and with it, its magnetic field, like an invisible ribbon wrapped around the star.
Stellar2026-07-301 minarXiv:2607.28089express
Twisted Crown: How a Magnetic Vortex Rewrites Sunspots
The solar corona lives its own turbulent life. Magnetic fields here are governed by the motions of the dense surface — the Sun's photosphere — but occasionally they rewrite the magnetic pattern themselves.
Exoplanets2026-07-282 minarXiv:2607.25542express
Three Cloud Layers of Jupiter
Jupiter's atmosphere resembles a layered cake, where each layer plays its role. Scientists took data from four instruments at once (VLT/MUSE, Cassini/VIMS, IRTF/SpeX, and Juno/JIRAM) and built a model of clouds and ammonia in the planet's equatorial zone, from 0.1 to 10 bar (pressure equivalent to hundreds of kilometers below Earth's…
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The Cosmic Bell: How Pulsations from the Sun to Stars Fade Away
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Lightning over a black hole: the first Neupert effect beyond our Galaxy
Active galactic nuclei (AGN) are the universe’s powerhouses: their X-ray coronae blaze millions of times hotter than stellar atmospheres. But what strikes the spark? A ten-day X-ray campaign by the XRISM and XMM-Newton satellites, aimed at NGC 3783, provided the answer: it’s actual thunderstorms.
Galaxies2026-06-053 minarXiv:2606.07741
Cosmic Latte: Why X-rays Are Three Times Brighter Than Hydrogen
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Space Physics2026-05-211 minarXiv:2605.24038express
Aurora Hunter: When the Sky Lights Up
The aurora borealis is like a distant theater: the show may be on, but whether the audience sees it depends on the curtain. Here, the curtain is clouds and moonlight. Earlier forecasts tried to predict both the occurrence of auroras and viewing conditions at once, mixing everything together.
Stellar2026-05-032 minarXiv:2605.01947express
The Magnetic Roots of the Solar Wind
The crown of a huge tree sways in the wind, but the roots and trunk are hidden underground. On the Sun, magnetic fields play the role of such invisible roots. They emerge from the depths, thread through the entire atmosphere, and govern the motion of the hot gas — plasma.
Stellar2026-04-281 minarXiv:2604.26003express
The X-ray Trail of the Solar Wind
The solar wind, a stream of charged particles from the Sun, slams into the tenuous gas that fills the space between the stars. The collision produces a faint X-ray glow. For astronomers, this is like fog in front of headlights: it obscures distant objects.
Atomic Physics2026-03-261 minarXiv:2603.25781express
Light Twisted into a Spiral Catches Magnetic Fields
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Stellar2026-03-231 minarXiv:2603.21885express
Solar Storms Trapped in a Cage
The Sun sometimes produces giant clouds of plasma that try to escape into space. But often they fail: an invisible magnetic cage keeps them near the surface. Such failed eruptions are called "trapped." Scientists built a computer model to understand exactly how this cage works.
Space Physics2026-03-111 minarXiv:2603.10760express
Beams from Jupiter's Poles
Above Jupiter's poles, auroras blaze as electrons are accelerated by electric fields and slam into the upper atmosphere, making the gas glow. But not all electrons head downward. Some, it turns out, get a kick in the opposite direction — away from the planet, into deep space.
HEP Phenomenology2026-03-101 minarXiv:2603.10189express
A Pulsar as a Beacon for Invisible Particles
A neutron star the size of a city spins thirty times per second. Its magnetic field is trillions of times stronger than Earth's. Such conditions could spawn a cloud of axions around the star — light particles that no detector has caught yet, but which neatly explain the hidden mass of the Universe.
High Energy2026-02-231 minarXiv:2602.20230express
A Magnetic Carousel Around a Dead Star
The VLA radio telescope peered into the Boomerang Nebula — a cloud inflated by the wind from a rapidly spinning neutron star. The new images reveal details as small as a lunar disk on the sky: an elongated core around the pulsar and a long arc curving around it from the north.
Stellar2026-02-021 minarXiv:2602.01742express
The Solar Knot That Unties Itself
The Sun frequently launches narrow plasma jets, coronal jets, that resemble fountains of superheated gas erupting from the star's atmosphere. One such eruption, which occurred on November 10, 2022, caught scientists' attention: it was accompanied by a C1.1-class flare and had an unusually wide cone.
Exoplanets2026-01-121 minarXiv:2601.07983express
When the Sun Dived into a Cloud
As it travels through the Galaxy, the Solar System occasionally dives into thick interstellar clouds — clumps of tenuous hydrogen and dust.
Stellar2025-12-031 minarXiv:2512.03611express
Solar Magnetic Poles: First Shots from Beyond the Equator
The Sun is not just a ball — it's a magnetic mansion. Its invisible force lines, like electrical wiring, thread through space and control space weather. But until now, we've only seen this wiring from the landing — the plane of Earth's orbit. The attic and basement, the magnetic poles, remained a mystery.
The Signature of Infalling Gas in the Light of a Newborn Planet
In 2022, the Subaru telescope photographed a point of light 100 astronomical units from the star AB Aurigae. The point was named planet AB Aur b, but debates did not subside: what exactly is glowing, the planet itself or dust around it?