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Glossary term: Aurora

Also known as Aurorae
Redirected from Aurora Australis

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 and solar flares 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.

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Term and definition status: This term and its definition is still awaiting approval

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 Comments 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 Comments 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 Comments 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 Comments 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 Comments 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 Comments Attribution 4.0 International (CC BY 4.0) icons