[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P20] Multi-event analysis of three-types of optical emissions at subauroral latitudes using ground optical and radio instruments and the Arase and Van Allen Probes satellites: Estimation of heat flux due to Coulomb collision

*Rei Sugimura¹, Kazuo Shiokawa¹, Yuichi Otsuka¹, Shin-ichiro Oyama¹, Martin G Connors², Akira Kadokura³, Alexey Poddelsky⁴, Igor Poddelsky⁴, Nozomu Nishitani¹, Simon G Shepherd⁵, J Michael Ruohoniemi⁶, Charles Smith⁷, Robert MacDowall⁸, Harlan Spence⁷, Geoff Reeves⁹, Herbert O Funsten ⁹, Yoshizumi Miyoshi¹, Iku Shinohara¹⁰, Yoshiya Kasahara¹¹, Fuminori Tsuchiya¹², Atsushi Kumamoto¹², Satoko Nakamura¹, Atsuki Shinbori¹, Kazushi Asamura¹³, Shoichiro Yokota¹⁴, Yoichi Kazama¹⁵, Chae-Woo Jun¹, Shiang-Yu Wang¹⁵, Sunny W.Y. Tam¹⁶, Satoshi Kasahara¹⁷, Kunihiro Keika¹⁸, Tomoaki Hori¹, Ayako Matsuoka¹⁰ (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.Athabasca University, 3.National Institute of Polar Research, 4.Institute of Cosmophysical Research and Radiowave Propagation, Far Eastern Branch of the Russian Academy of Sciences, 5.Thayer School of Engineering, Dartmouth College, 6.Bradley Department of Electrical and Computer Engineering, Virginia Tech, 7.Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, 8.NASA Goddard Space Flight Center, Greenbelt, 9.Los Alamos National Laboratory, 10.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 11.Graduate School of Natural Science and Technology, Kanazawa University, 12.Graduate School of Science, Tohoku University, 13.Japan Aerospace Exploration Agency, 14.Department of Earth and Space Science, Graduate School of Science, Osaka University, 15.Academia Sinica Institute of Astronomy and Astrophysics, 16.Institute of Space and Plasma Sciences, National Cheng Kung University, 17.Department of Earth and Planetary Science, School of Science, University of Tokyo, 18.Graduate School of Science, Tokyo University)

Keywords:STEVE, SAR arc, Arase satellite

Strong Thermal Emission Velocity Enhancement (STEVE) is a latitudinally-narrow, purple band of emission seen at subauroral latitudes, which was discovered in 2016. Well-known Stable Auroral Red (SAR) arcs also occurs at subauroral latitude. Red and green arcs, which are similar to SAR arcs at subauroral latitudes but accompanied by green (557.7 nm) emission, have also been reported. However, the characteristics of the magnetospheric plasma and electromagnetic field variations as a source of these three types of optical emissions have not fully been studied, because of limited conjugate observations between magnetospheric satellites and ground-based optical and radio instruments. In this study, we report the auroral morphology as seen in all-sky image data obtained at seven ground stations (Athabasca, Gakona, Husafell, Kapuskasing, Magadan, Nyrola and Tromsø) during about four years from January 2017 to April 2021. By referring to the optical images as well as the ionospheric footprint of magnetospheric satellites (Arase and Van Allen Probes) calculated with the Tsyganenko magnetic field model (TS04), we have identified four cases of STEVE, four cases of SAR arc, three cases of green and red arcs in which these satellites were located in the conjugate regions in the magnetosphere of the optical emissions. For all three types of optical emissions, satellite data showed that the plasmasphere and ring-current particles spatially overlapped in the conjugate regions of the magnetosphere. Some electromagnetic waves in mHz to kHz were observed for STEVE and red and green arc events. SuperDARN radar data showed a strong westward plasma flow in the ionosphere, especially during the STEVE events, while the plasma flows associated with SAR arcs and red and green arcs are relatively weak and variable. Heat fluxes due to Coulomb collisions were larger for STEVE compared to SAR arc. However, the heat flux may have been underestimated for events that low-energy electrons were not measured. These analyses have provided the first-ever comparison of magnetospheric particle and electromagnetic field characteristics for the three types of optical emissions in the subauroral region. In the presentation, we will discuss the differences and similarities of the magnetospheric and ionospheric processes responsible for producing these three-types of emissions.