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Glossary term: Ionisation

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Description: L'ionisation est le processus de soustraction ou d'ajout d'électrons à des atomes auparavant neutres, transformant ainsi un gaz d'atomes (ou de molécules) neutres en un gaz composé d'ions chargés, c'est-à-dire un plasma.

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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

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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


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


La partie gauche de l'image montre un ciel d'un vert éclatant. La partie droite présente un ciel plus sombre, mais avec des traînées vertes.

Aurore multicolore en Islande, par Marco Migliardi pour l'Associazione Astronomica Cortina, Italie

Caption: Première place au concours d'astrophotographie 2021 de l'IAU OAE, catégorie Aurores (images fixes) Les aurores sont le résultat de processus d'ionisation et d'excitation dans la haute atmosphère terrestre, causés par des particules chargées provenant du vent solaire ou d'éjections de masse coronale. Les différentes couleurs d'une aurore indiquent les espèces d'atomes et de molécules atmosphériques impliquées. La couleur la plus courante est le vert vif, qui, avec le rouge profond, provient de l'oxygène atomique. Les teintes bleues, violettes et roses sont beaucoup plus rares et proviennent de l'azote moléculaire. La réflexion de l'aurore dans l'eau indique la luminosité des aurores intenses à des latitudes plus élevées.
Credit: Marco Migliardi au nom de l'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.
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License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons

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