Active auroral arc powered by accelerated electrons from very high altitudes

Abstract Bright, discrete, thin auroral arcs are a typical form of auroras in nightside polar regions. Their light is produced by magnetospheric electrons, accelerated downward to obtain energies of several kilo electron volts by a quasi-static electric field. These electrons collide with and excite...

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Autores principales:	Shun Imajo, Yoshizumi Miyoshi, Yoichi Kazama, Kazushi Asamura, Iku Shinohara, Kazuo Shiokawa, Yoshiya Kasahara, Yasumasa Kasaba, Ayako Matsuoka, Shiang-Yu Wang, Sunny W. Y. Tam, Tzu‑Fang Chang, Bo‑Jhou Wang, Vassilis Angelopoulos, Chae-Woo Jun, Masafumi Shoji, Satoko Nakamura, Masahiro Kitahara, Mariko Teramoto, Satoshi Kurita, Tomoaki Hori
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/d14d902323da45109a1842312ec18a2b
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spelling	oai:doaj.org-article:d14d902323da45109a1842312ec18a2b2021-12-02T13:51:16ZActive auroral arc powered by accelerated electrons from very high altitudes10.1038/s41598-020-79665-52045-2322https://doaj.org/article/d14d902323da45109a1842312ec18a2b2021-01-01T00:00:00Zhttps://doi.org/10.1038/s41598-020-79665-5https://doaj.org/toc/2045-2322Abstract Bright, discrete, thin auroral arcs are a typical form of auroras in nightside polar regions. Their light is produced by magnetospheric electrons, accelerated downward to obtain energies of several kilo electron volts by a quasi-static electric field. These electrons collide with and excite thermosphere atoms to higher energy states at altitude of ~ 100 km; relaxation from these states produces the auroral light. The electric potential accelerating the aurora-producing electrons has been reported to lie immediately above the ionosphere, at a few altitudes of thousand kilometres1. However, the highest altitude at which the precipitating electron is accelerated by the parallel potential drop is still unclear. Here, we show that active auroral arcs are powered by electrons accelerated at altitudes reaching greater than 30,000 km. We employ high-angular resolution electron observations achieved by the Arase satellite in the magnetosphere and optical observations of the aurora from a ground-based all-sky imager. Our observations of electron properties and dynamics resemble those of electron potential acceleration reported from low-altitude satellites except that the acceleration region is much higher than previously assumed. This shows that the dominant auroral acceleration region can extend far above a few thousand kilometres, well within the magnetospheric plasma proper, suggesting formation of the acceleration region by some unknown magnetospheric mechanisms.Shun ImajoYoshizumi MiyoshiYoichi KazamaKazushi AsamuraIku ShinoharaKazuo ShiokawaYoshiya KasaharaYasumasa KasabaAyako MatsuokaShiang-Yu WangSunny W. Y. TamTzu‑Fang ChangBo‑Jhou WangVassilis AngelopoulosChae-Woo JunMasafumi ShojiSatoko NakamuraMasahiro KitaharaMariko TeramotoSatoshi KuritaTomoaki HoriNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-8 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Shun Imajo Yoshizumi Miyoshi Yoichi Kazama Kazushi Asamura Iku Shinohara Kazuo Shiokawa Yoshiya Kasahara Yasumasa Kasaba Ayako Matsuoka Shiang-Yu Wang Sunny W. Y. Tam Tzu‑Fang Chang Bo‑Jhou Wang Vassilis Angelopoulos Chae-Woo Jun Masafumi Shoji Satoko Nakamura Masahiro Kitahara Mariko Teramoto Satoshi Kurita Tomoaki Hori Active auroral arc powered by accelerated electrons from very high altitudes
description	Abstract Bright, discrete, thin auroral arcs are a typical form of auroras in nightside polar regions. Their light is produced by magnetospheric electrons, accelerated downward to obtain energies of several kilo electron volts by a quasi-static electric field. These electrons collide with and excite thermosphere atoms to higher energy states at altitude of ~ 100 km; relaxation from these states produces the auroral light. The electric potential accelerating the aurora-producing electrons has been reported to lie immediately above the ionosphere, at a few altitudes of thousand kilometres1. However, the highest altitude at which the precipitating electron is accelerated by the parallel potential drop is still unclear. Here, we show that active auroral arcs are powered by electrons accelerated at altitudes reaching greater than 30,000 km. We employ high-angular resolution electron observations achieved by the Arase satellite in the magnetosphere and optical observations of the aurora from a ground-based all-sky imager. Our observations of electron properties and dynamics resemble those of electron potential acceleration reported from low-altitude satellites except that the acceleration region is much higher than previously assumed. This shows that the dominant auroral acceleration region can extend far above a few thousand kilometres, well within the magnetospheric plasma proper, suggesting formation of the acceleration region by some unknown magnetospheric mechanisms.
format	article
author	Shun Imajo Yoshizumi Miyoshi Yoichi Kazama Kazushi Asamura Iku Shinohara Kazuo Shiokawa Yoshiya Kasahara Yasumasa Kasaba Ayako Matsuoka Shiang-Yu Wang Sunny W. Y. Tam Tzu‑Fang Chang Bo‑Jhou Wang Vassilis Angelopoulos Chae-Woo Jun Masafumi Shoji Satoko Nakamura Masahiro Kitahara Mariko Teramoto Satoshi Kurita Tomoaki Hori
author_facet	Shun Imajo Yoshizumi Miyoshi Yoichi Kazama Kazushi Asamura Iku Shinohara Kazuo Shiokawa Yoshiya Kasahara Yasumasa Kasaba Ayako Matsuoka Shiang-Yu Wang Sunny W. Y. Tam Tzu‑Fang Chang Bo‑Jhou Wang Vassilis Angelopoulos Chae-Woo Jun Masafumi Shoji Satoko Nakamura Masahiro Kitahara Mariko Teramoto Satoshi Kurita Tomoaki Hori
author_sort	Shun Imajo
title	Active auroral arc powered by accelerated electrons from very high altitudes
title_short	Active auroral arc powered by accelerated electrons from very high altitudes
title_full	Active auroral arc powered by accelerated electrons from very high altitudes
title_fullStr	Active auroral arc powered by accelerated electrons from very high altitudes
title_full_unstemmed	Active auroral arc powered by accelerated electrons from very high altitudes
title_sort	active auroral arc powered by accelerated electrons from very high altitudes
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/d14d902323da45109a1842312ec18a2b
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Active auroral arc powered by accelerated electrons from very high altitudes

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