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Glossary term: Aurora

Also known as Aurorae

Description: An aurora is a display of diffuse variable-color light in Earth's atmosphere, mainly in the polar regions. In the north it is known as the Northern Lights or aurora borealis, in the south, Southern Lights or aurora australis. The aurorae vary in color from greenish-white to red, mainly occur at altitudes of about 100 kilometers, and form around two irregular auroral ovals centered on Earth's magnetic poles. They occur when charged particles from the solar wind or coronal mass ejections (CMEs) are trapped in Earth's magnetosphere, concentrated by magnetic fields in the upper atmosphere, and spiral along Earth's magnetic field lines toward the poles. Their interactions with atmospheric atoms and molecules produce the auroral emissions. This effect is enhanced during times of high solar activity. Aurora have also been observed on other planets in the Solar System notably on Jupiter and Saturn.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

Related Media


A Y-shaped band of light with light and dark patches, in the colours green and pink glows in the sky over some buildings

Till the End of the World, by Hang Li, China

Caption: First place in the 2021 IAU OAE Astrophotography Contest, category Aurorae (time-lapses). Aurorae are often called "Northern Lights" in Europe or North America but here we see that they also exist at the extreme south of our planet. Taken at Zhongshan Station, Antarctica, this time-lapse (speeded up) video shows how some bands of Aurora can remain stable over longer times while other features appear to "dance". See how many different patterns of swirls and waves you can spot in the video.
Credit: Hang Li/IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


An all-sky image with the sky as a dark blue circle. A curved band of light stretches from top to bottom

Under the Stars with Steve, by Sheila Wiwchar, Canada

Caption: Third place in the 2021 IAU OAE Astrophotography Contest, category Aurorae (time-lapses). This is a strange atmospheric phenomenon known as Steve. This is similar to an aurora as it is caused by charged particles interacting with the Earth's magnetic field. However unlike aurorae, the particles which cause Steve are generated high in the Earth's atmosphere rather than coming from the Sun. Note the banded "picket fence" appearance. This is caused by waves of these particles in the upper atmosphere. The name Steve was chosen by the first group to describe this phenomenon as a familiar name for something unknown. Sheila Wiwchar/IAU OAE
Credit: Wiwchar, Sheila; IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Curved green bands of light radiate out from the horizon, diffusing to wider bands at the top of the image.

Icelandic Rivers of Light, by Sergio Díaz Ruiz, Spain

Caption: Second place in the 2021 IAU OAE Astrophotography Contest, category Aurorae (time-lapses) This video shows how aurorae evolve slowly over timescales of a few minutes. Note the clouds being illuminated from behind in the last two shots. Aurorae are caused by interactions between the charged particles blown out in huge explosions from the Sun and the Earth's magnetic field. The changes over time are caused by huge waves of particles pushing the Earth's magnetic field into strange shapes before it snaps back into place.
Credit: Sergio Díaz Ruiz/IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


The left side of the image shows the sky glowing green. The right side has a darker sky but has green streaks

Multicolored aurora in Iceland, by Marco Migliardi on behalf of Associazione Astronomica Cortina, Italy

Caption: First place in the 2021 IAU OAE Astrophotography Contest, category Aurorae (still images) Aurorae are the result of ionisation and excitation processes in Earth's upper atmosphere, caused by charged particles from the solar wind or from coronal mass ejections. The different colours in an aurora display indicate the species of atmospheric atoms and molecules involved. The most common colour is a bright green, which, together with deep red, originates from atomic oxygen. Blue, purple and pink hues are much rarer and originate from molecular nitrogen. The reflection of the aurora in the water indicates the brightness of intense aurorae at higher latitudes.
Credit: Marco Migliardi on behalf of Associazione Astronomica Cortina/IAU OAE.

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


A green, curved, y-shaped band of light over a mountainous horizon

Northern light dragon over Ersfjordbotn/Norway

Caption: Second place in the 2021 IAU OAE Astrophotography Contest, category Aurorae (still images) Aurorae often display waving curtain-like patterns where arcs or bands form moving curls, folds, or even spirals. These irregular shapes mirror the small-scale structure of Earth's magnetic field interacting with charged particle flows. Although the full Moon illuminates both the landscape and the night sky, the auroa is easily visible, which demonstrates that it can be a very bright and colourful phenomenon.
Credit: Rainer Sparenberg/IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Wavy horizontal green bands, punctuated by dark vertical stripes. almost appear to rain down on a watery landscape

Iceland aurora, by Emanuele Balboni, Italy

Caption: Third place in the 2021 IAU OAE Astrophotography Contest, category Aurorae (still images) The blurred motions of the aurora caught during the exposure time of this photograph beautifully illustrate its dynamic nature. While certain forms of aurorae, like homogeneous arcs and bands or diffuse glows, can remain static for hours, others, like rayed arcs or bands (also called "curtains"), can change within seconds in shape and brightness.
Credit: Emanuele Balboni/IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Two illuminated teepees in a subarctic forest. Green bands of aurorae light up the sky.

Northern Lights - Teepees

Caption: Taken with a smartphone at Cassidy Point, Yellowknife, Canada, on 24 March 2023, this stunning display captured the ethereal Northern Lights painting the night sky. The biting cold of -20°F (-29°C) set the stage for the vibrant hues of the Aurora Borealis, a celestial ballet created by collisions between charged solar particles and the Earth's atmosphere. The Earth’s magnetic field directs the charged particles towards the polar regions, where they interact with the various atoms and molecules in the atmosphere. This natural phenomenon transforms the sky into a canvas of radiant greens, pinks, and purples, casting a mesmerising glow above. The different colours of an aurora are determined by the gases in Earth’s atmosphere, the altitude where the aurora occurs, the density of the atmosphere, and the energy of the charged particles. In general, green is attributed to oxygen molecules, red is associated with high-altitude oxygen molecules, purple and blue are associated with hydrogen and helium, and pink aurorae are typically associated with nitrogen. Against this cosmic backdrop, the teepees of Aurora Village below provide a tranquil contrast to the celestial spectacle unfolding overhead. Preserving the pristine darkness of this location ensures the continued splendour of such awe-inspiring natural light shows.
Credit: Oanh Vuong/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


The sky rotates around one star that appears fixed. Bubbles and swirls of green aurorae fill the foreground

The Big Dipper in the Polar Night

Caption: Step into the cosmic theatre of Iceland’s northern skies in this time-lapse where the illustrious Big Dipper commands attention, tracing an almost complete circle around Polaris — an exquisite sight that is not visible from mid-latitudes. This time-lapse, captured through fisheye lenses, reveals the timeless choreography of the Big Dipper, vividly illustrating its celestial waltz. Amidst this spectacle, the Arctic night reveals its grandeur, painting a panoramic canvas that showcases not just the celestial journey of this iconic asterism but also the ethereal dance of the Northern Lights. In this breathtaking tapestry, the Big Dipper takes centre stage against the mesmerising backdrop of the Icelandic nightscape, adorned by the vibrant hues of the Aurora Borealis.
Credit: Stephanie Ziyi Ye/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


A green wisp of light rises over an illuminated lighthouse

Fire of the Sky

Caption: In the serene landscapes of Lofoten, Norway on 28 March 2023, the sky was set ablaze by the aurora. The Northern (Southern) Lights, also known as aurorae, are natural light displays resulting from interactions between solar winds and Earth’s magnetic fields, as charged particles are redirected towards the north and south pole regions. In Norse legends, they are often depicted as a heavenly fire. In this scene, the celestial show is beautifully complemented by the silhouette of a lighthouse, as if the lighthouse ignited the mesmerising display overhead. Caught off-guard by this dazzling spectacle, the photographer swiftly captured the moment with a smartphone. This is a testament to the breathtaking surprises nature offers and the impressive capabilities of modern devices.
Credit: Stephanie Ziyi Ye/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Ripples of green light over a tree-lined horizon. Pillars of white light rise into the sky.

Northern Lights Color

Caption: This photograph taken with a smartphone captures the ethereal beauty of the Northern Lights at Cassidy Point, Yellowknife, NT, Canada on 24 March 2023, at temperatures well below freezing (–29°C). The mesmerising dance of the Aurora Borealis (Australis), commonly known as the Northern (Southern) Lights, paints the night sky in striking hues. The aurora is a natural phenomenon caused by charged particles from the Sun interacting with Earth’s atmosphere, and being redirected by Earth’s magnetic field towards the north and south polar regions. The charged particles excite atoms and molecules in the atmosphere, resulting in a light display that varies in colour and form. The different colours of an aurora are determined by the gases (atoms and molecules) in Earth's atmosphere, the altitude of the aurora, the density of the atmosphere, and the energy of the charged particles. In general, green is attributed to oxygen molecules, red is associated with high-altitude oxygen molecules, purple and blue are associated with hydrogen and helium, and pink auroras are typically associated with nitrogen. On this particular night, the serene environment of Cassidy Point provided an unobstructed view of the lights. In the foreground, Aurora Village can be seen, a site renowned for organised tours to witness this spectacle.
Credit: Jason Johnson/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons

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