TY - JOUR
T1 - Observation of Source Plasma and Field Variations of a Substorm Brightening Aurora at L ∼ 6 by a Ground-Based Camera and the Arase Satellite on 12 October 2017
AU - Chen, L.
AU - Shiokawa, K.
AU - Miyoshi, Y.
AU - Oyama, S.
AU - Jun, C. W.
AU - Ogawa, Y.
AU - Hosokawa, K.
AU - Inaba, Y.
AU - Kazama, Y.
AU - Wang, S. Y.
AU - Tam, S. W.Y.
AU - Chang, T. F.
AU - Wang, B. J.
AU - Asamura, K.
AU - Kasahara, S.
AU - Yokota, S.
AU - Hori, T.
AU - Keika, K.
AU - Kasaba, Y.
AU - Kumamoto, A.
AU - Tsuchiya, F.
AU - Shoji, M.
AU - Kasahara, Y.
AU - Matsuoka, A.
AU - Shinohara, I.
AU - Imajo, S.
AU - Nakamura, S.
AU - Kitahara, M.
N1 - 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. This work was supported by Grants‐in‐Aid for Scientific Research (15H05815, 16H06286, and 20H01959) from the Japan Society for the Promotion of Science. Most of the data analysis was conducted using the Space Physics Environment Data Analysis System (SPEDAS) tool (Angelopoulos et al., 2019 ).
Publisher Copyright:
© 2022. American Geophysical Union. All Rights Reserved.
PY - 2022/11
Y1 - 2022/11
N2 - Auroral brightening is one of the most common phenomena that occur during substorm onset and is usually recognized as a projection of the substorm-associated magnetospheric plasma dynamics to the ionosphere. However, electromagnetic fields and plasma features associated with the substorm brightening arc have not been well understood. In this study, we present a comprehensive observation of the source plasma and field variations of a substorm brightening aurora in the inner magnetosphere. We performed a unique conjugate observation of a substorm brightening auroral arc observed by a ground-based camera and by the Arase satellite in the magnetospheric source region at L ∼ 6. The event was observed at Tromsø (69.6°N, 19.2°E), Norway, on 12 October 2017. The brightening arc indicates east-west structures with longitudinal scales of ∼0.5°–2.0°. Field-aligned bi-directional electrons with an energy range between 66 and 1,800 eV were detected by the satellite, simultaneously with the appearance of the brightening arc in the camera. These electrons were probably supplied from the auroral brightening region in the ionosphere, indicating that the satellite was on the same field line of the brightening aurora. The magnetic and electric field data show characteristic fluctuations and earthward Poynting flux around the time that the satellite crossed the aurora. Anti-phase oscillations between the thermal pressure and the magnetic pressure are also reported. Based on these observations, we suggest the possibility that a ballooning instability occurred in the source region of the substorm brightening arc in the inner magnetosphere at L ∼ 6.
AB - Auroral brightening is one of the most common phenomena that occur during substorm onset and is usually recognized as a projection of the substorm-associated magnetospheric plasma dynamics to the ionosphere. However, electromagnetic fields and plasma features associated with the substorm brightening arc have not been well understood. In this study, we present a comprehensive observation of the source plasma and field variations of a substorm brightening aurora in the inner magnetosphere. We performed a unique conjugate observation of a substorm brightening auroral arc observed by a ground-based camera and by the Arase satellite in the magnetospheric source region at L ∼ 6. The event was observed at Tromsø (69.6°N, 19.2°E), Norway, on 12 October 2017. The brightening arc indicates east-west structures with longitudinal scales of ∼0.5°–2.0°. Field-aligned bi-directional electrons with an energy range between 66 and 1,800 eV were detected by the satellite, simultaneously with the appearance of the brightening arc in the camera. These electrons were probably supplied from the auroral brightening region in the ionosphere, indicating that the satellite was on the same field line of the brightening aurora. The magnetic and electric field data show characteristic fluctuations and earthward Poynting flux around the time that the satellite crossed the aurora. Anti-phase oscillations between the thermal pressure and the magnetic pressure are also reported. Based on these observations, we suggest the possibility that a ballooning instability occurred in the source region of the substorm brightening arc in the inner magnetosphere at L ∼ 6.
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U2 - 10.1029/2021JA030072
DO - 10.1029/2021JA030072
M3 - Article
AN - SCOPUS:85142620736
SN - 2169-9402
VL - 127
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
IS - 11
M1 - e2021JA030072
ER -