University of Oulu

Inaba, Y., Shiokawa, K., Oyama, S.‐i., Otsuka, Y., Oksanen, A., Shinbori, A., et al. (2020). Plasma and field observations in the magnetospheric source region of a stable auroral red (SAR) arc by the Arase satellite on 28 March 2017. Journal of Geophysical Research: Space Physics, 125, e2020JA028068.

Plasma and field observations in the magnetospheric source region of a stable auroral red (SAR) arc by the Arase satellite on 28 March 2017

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Author: Inaba, Yudai1; Shiokawa, Kazuo1; Oyama, Shin‐ichiro1,2,3;
Organizations: 1Institute for Space‐Earth Environmental Research, Nagoya University, Nagoya, Japan
2Ionosphere Research Unit, University of Oulu, Oulu, Finland
3National Institute of Polar Research, Tokyo, Japan
4Jyväskylän Sirius ry, Jyväskylä, Finland
5Institute of Physics and Technologies, North‐Eastern Federal University, Yakutsk, Russia
6Academia Sinica Institute of Astronomy and Astrophysics, Taipei, Taiwan
7Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan, Taiwan
8Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Japan
9Department of Earth and Planetary Science, School of Science, University of Tokyo, Tokyo, Japan
10Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa, Japan
11Graduate School of Natural Science and Technology, Kanazawa University, Kakuma‐machi, Kanazawa, Japan
12Graduate School of Science, Tohoku University, Sendai, Japan
13Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Potsdam, Germany
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 5.4 MB)
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Language: English
Published: American Geophysical Union, 2020
Publish Date: 2021-03-21


A stable auroral red (SAR) arc is an aurora with a dominant 630 nm emission at subauroral latitudes. SAR arcs have been considered to occur due to the spatial overlap between the plasmasphere and the ring‐current ions. In the overlap region, plasmaspheric electrons are heated by ring‐current ions or plasma waves, and their energy is then transferred down to the ionosphere where it causes oxygen red emission. However, there have been no study conducted so far that quantitatively examined plasma and electromagnetic fields in the magnetosphere associated with SAR arc. In this paper, we report the first quantitative evaluation of conjugate measurements of a SAR arc observed at 2204 UT on 28 March 2017 and investigate its source region using an all‐sky imager at Nyrölä (magnetic latitude: 59.4°N), Finland, and the Arase satellite. The Arase observation shows that the SAR arc appeared in the overlap region between a plasmaspheric plume and the ring‐current ions and that electromagnetic ion cyclotron waves and kinetic Alfven waves were not observed above the SAR arc. The SAR arc was located at the ionospheric trough minimum identified from a total electron content map obtained by the GNSS receiver network. The Swarm satellite flying in the ionosphere also passed the SAR arc at ~2320 UT and observed a decrease in electron density and an increase in electron temperature during the SAR‐arc crossing. These observations suggest that the heating of plasmaspheric electrons via Coulomb collision with ring‐current ions is the most plausible mechanism for the SAR‐arc generation.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 125
Issue: 10
Article number: e2020JA028068
DOI: 10.1029/2020JA028068
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: This work was supported by Grants‐in‐Aid for Scientific Research (15H05815, 15H05747, 16H06286, 17H00728, and 20H01959) and by Birateral Program (JPJSBP120194814) from the Japan Society for the Promotion of Science. Part of the work of YM, TH, and MS was performed at ERG‐SC.
Dataset Reference: Data Availability Statement: Swarm data were provided by ESA and are available online ( The SYM‐H, AU, and AL indices were provided by World Data Center (WDC) for Geomagnetism at Kyoto University, Japan. Scientific data of the ERG (Arase) satellite were obtained from the ERG Science Center (ERG‐SC) operated by ISAS/JAXA and ISEE/Nagoya University (, Miyoshi, Hori, et al., 2018). The present study analyzed LEP‐e‐L2 v02_02 data, MEP‐i‐L2 v02_00 data, PWE/EFD/E_spin‐L2 v03_01 data, PWE/EFD/pot‐L2 v03_01 data, PWE/HFA‐L2 v01_01 and MGF‐L2 v03_04 data, MGF/64 Hz‐L2 v03_03 data, and L2 v02 orbit data. The optical data from Nyrölä are available from the ISEE through the ERG‐SC. The PWING observation data and geomagnetic indices (AE and SYM‐H) are distributed by the Inter‐university Upper atmosphere Global Observation Network (IUGONET) project of the Ministry of Education, Culture, Sports, Science and Technology of Japan. The OMNI data were provided by the GSFC/SPDF OMNIWeb interface ( The solar wind parameters and W‐parameters for driving TS05 model were provided by TS05 web repository ( The GNSS‐TEC data providers are listed at
Copyright information: © 2020. American Geophysical Union.