Multi-Event Analysis of Plasma and Field Variations in Source of Stable Auroral Red (SAR) Arcs in Inner Magnetosphere During Non-Storm-Time Substorms

Yudai Inaba, Kazuo Shiokawa, Shin ichiro Oyama, Yuichi Otsuka, Martin Connors, Ian Schofield, Yoshizumi Miyoshi, Shun Imajo, Atsuki Shinbori, Artem Yu Gololobov, Yoichi Kazama, Shiang Yu Wang, Sunny W.Y. Tam, Tzu Fang Chang, Bo Jhou Wang, Kazushi Asamura, Shoichiro Yokota, Satoshi Kasahara, Kunihiro Keika, Tomoaki HoriAyako Matsuoka, Yoshiya Kasahara, Atsushi Kumamoto, Shoya Matsuda, Yasumasa Kasaba, Fuminori Tsuchiya, Masafumi Shoji, Masahiro Kitahara, Satoko Nakamura, Iku Shinohara, Harlan E. Spence, Geoff D. Reeves, Robert J. Macdowall, Charles W. Smith, John R. Wygant, John W. Bonnell

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Abstract

Stable auroral red (SAR) arcs are optical events with dominant 630.0-nm emission caused by low-energy electron heat flux into the topside ionosphere from the inner magnetosphere. SAR arcs are observed at subauroral latitudes and often occur during the recovery phase of magnetic storms and substorms. Past studies concluded that these low-energy electrons were generated in the spatial overlap region between the outer plasmasphere and ring-current ions and suggested that Coulomb collisions between plasmaspheric electrons and ring-current ions are more feasible for the SAR-arc generation mechanism rather than Landau damping by electromagnetic ion cyclotron waves or kinetic Alfvén waves. This work studies three separate SAR-arc events with conjunctions, using all-sky imagers and inner magnetospheric satellites (Arase and Radiation Belt Storm Probes [RBSP]) during non-storm-time substorms on December 19, 2012 (event 1), January 17, 2015 (event 2), and November 4, 2019 (event 3). We evaluated for the first time the heat flux via Coulomb collision using full-energy-range ion data obtained by the satellites. The electron heat fluxes due to Coulomb collisions reached ∼109 eV/cm2/s for events 1 and 2, indicating that Coulomb collisions could have caused the SAR arcs. RBSP-A also observed local enhancements of 7–20-mHz electromagnetic wave power above the SAR arc in event 2. The heat flux for the freshly detached SAR arc in event 3 reached ∼108 eV/cm2/s, which is insufficient to have caused the SAR arc. In event 3, local flux enhancement of electrons (<200 eV) and various electromagnetic waves were observed, these are likely to have caused the freshly detached SAR arc.

Original languageEnglish (US)
Article numbere2020JA029081
JournalJournal of Geophysical Research: Space Physics
Volume126
Issue number4
DOIs
StatePublished - Mar 12 2021

Bibliographical note

Funding Information:
The authors thank Y. Katoh, H. Hamaguchi, Y. Yamamoto, and T. Adachi of ISEE, Nagoya University for their continuous support of the all-sky imager operation. The authors also thank the RBSP/EMFISIS team for providing the data. The operation of the airglow imager at Gakona was supported by the University of Alaska, Fairbanks. Athabasca University GeoSpace Observatory was constructed and is operated with support from the Canada Foundation for Innovation. This work was supported by Grants-in-Aid for Scientific Research (15H05815, 15H05747, 16H06286, 20H01959, and 20H01955) from the Japan Society for the Promotion of Science. Part of the work of Y. Miyoshi, T. Hori, and M. Shoji was performed at ERG-SC. Most of the data analysis for satellites and imagers was conducted using the Space Physics Environment Data Analysis Software (SPEDAS) tool (Angelopoulos et?al.,?2019).

Funding Information:
The authors thank Y. Katoh, H. Hamaguchi, Y. Yamamoto, and T. Adachi of ISEE, Nagoya University for their continuous support of the all‐sky imager operation. The authors also thank the RBSP/EMFISIS team for providing the data. The operation of the airglow imager at Gakona was supported by the University of Alaska, Fairbanks. Athabasca University GeoSpace Observatory was constructed and is operated with support from the Canada Foundation for Innovation. This work was supported by Grants‐in‐Aid for Scientific Research (15H05815, 15H05747, 16H06286, 20H01959, and 20H01955) from the Japan Society for the Promotion of Science. Part of the work of Y. Miyoshi, T. Hori, and M. Shoji was performed at ERG‐SC. Most of the data analysis for satellites and imagers was conducted using the Space Physics Environment Data Analysis Software (SPEDAS) tool (Angelopoulos et al., 2019 ).

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.

Keywords

  • Arase
  • RBSP
  • SAR arc
  • non-storm-time substorm
  • plasmapause
  • ring current

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