Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation

Abstract Unlike the nightside aurora, which is controlled mainly by magnetic field reconnection in the magnetotail, the dayside aurora is closely associated with magnetic field merging at the dayside magnetopause. About two decades ago, it was discovered that the aurora is also controlled by solar i...

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Autores principales:	Kan Liou, Elizabeth J. Mitchell
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2020
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/f548d962fe4d433a816453e8e4202b95
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spelling	oai:doaj.org-article:f548d962fe4d433a816453e8e4202b952021-12-02T16:43:42ZHemispheric asymmetry of the dayside aurora due to imbalanced solar insolation10.1038/s41598-020-70018-w2045-2322https://doaj.org/article/f548d962fe4d433a816453e8e4202b952020-08-01T00:00:00Zhttps://doi.org/10.1038/s41598-020-70018-whttps://doaj.org/toc/2045-2322Abstract Unlike the nightside aurora, which is controlled mainly by magnetic field reconnection in the magnetotail, the dayside aurora is closely associated with magnetic field merging at the dayside magnetopause. About two decades ago, it was discovered that the aurora is also controlled by solar insolation. Because the finding was based on data acquired mainly in the Northern Hemisphere, an outstanding question is if the auroral solar insolation effect also exists in the Southern Hemisphere. The present study addresses this question by studying dayside auroras from both hemispheres. We analyze 6 years’ worth of Earth disk emissions at far ultraviolet wavelengths acquired by the Global UltraViolet Imager on-board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite from 2002 to 2007. It is found that the solar insolation effect also exists in the Southern Hemisphere. In essence, the energy flux deposited as electron precipitation, is larger when the polar hemisphere is sunlit and is smaller when the polar hemisphere is dark. Because auroras are produced mainly by electron precipitation and because electrons are the main current carrier, this north–south asymmetry is consistent with the previous finding that larger (smaller) field-aligned currents are flowing out of the sunlit (dark) hemisphere. This trend is independent of the solar wind driving, suggesting that it is an effect associated with solar insolation. A small north–south asymmetry in the dayside auroral energy flux was identified. We discuss the asymmetry in the context of magnetospheric current and voltage generators.Kan LiouElizabeth J. MitchellNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 10, Iss 1, Pp 1-8 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Kan Liou Elizabeth J. Mitchell Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation
description	Abstract Unlike the nightside aurora, which is controlled mainly by magnetic field reconnection in the magnetotail, the dayside aurora is closely associated with magnetic field merging at the dayside magnetopause. About two decades ago, it was discovered that the aurora is also controlled by solar insolation. Because the finding was based on data acquired mainly in the Northern Hemisphere, an outstanding question is if the auroral solar insolation effect also exists in the Southern Hemisphere. The present study addresses this question by studying dayside auroras from both hemispheres. We analyze 6 years’ worth of Earth disk emissions at far ultraviolet wavelengths acquired by the Global UltraViolet Imager on-board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite from 2002 to 2007. It is found that the solar insolation effect also exists in the Southern Hemisphere. In essence, the energy flux deposited as electron precipitation, is larger when the polar hemisphere is sunlit and is smaller when the polar hemisphere is dark. Because auroras are produced mainly by electron precipitation and because electrons are the main current carrier, this north–south asymmetry is consistent with the previous finding that larger (smaller) field-aligned currents are flowing out of the sunlit (dark) hemisphere. This trend is independent of the solar wind driving, suggesting that it is an effect associated with solar insolation. A small north–south asymmetry in the dayside auroral energy flux was identified. We discuss the asymmetry in the context of magnetospheric current and voltage generators.
format	article
author	Kan Liou Elizabeth J. Mitchell
author_facet	Kan Liou Elizabeth J. Mitchell
author_sort	Kan Liou
title	Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation
title_short	Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation
title_full	Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation
title_fullStr	Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation
title_full_unstemmed	Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation
title_sort	hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation
publisher	Nature Portfolio
publishDate	2020
url	https://doaj.org/article/f548d962fe4d433a816453e8e4202b95
work_keys_str_mv	AT kanliou hemisphericasymmetryofthedaysideauroraduetoimbalancedsolarinsolation AT elizabethjmitchell hemisphericasymmetryofthedaysideauroraduetoimbalancedsolarinsolation
_version_	1718383550042996736

Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation

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