[P-EM11] Dynamics of the Inner Magnetospheric System

[PEM11-12] Multi-event analysis of three-types of optical emissions at subauroral latitudes using ground-based all-sky images and the Arase and Van Allen Probes satellites

*Rei Sugimura¹, Kazuo Shiokawa¹, Yuichi Otsuka¹, Shin-ichiro Oyama¹, Martin G Connors², Akira Kadokura³, Alexey Poddelsky⁴, Igor Poddelsky⁴, Boris Shevtsov⁴, Yoshizumi Miyoshi¹, Iku Shinohara⁸, Fuminori Tsuchiya¹, Yoshiya Kasahara⁹, Atsushi Kumamoto¹⁰, Satoko Nakamura¹, Atsuki Shinbori¹, Kazushi Asamura^7,11, Shoichiro Yokota¹², Kunihiro Keika¹⁵, Tomoaki Hori¹, Yoichi Kazama¹³, Jun C.-W¹, Satoshi Kasahara¹⁴, Ayako Matsuoka⁸, Charles Smith⁵, Robert Macdowall⁶, Harlan Spence⁵, Geoff Reeve⁷, Herbert O Funsten⁷, Nozomu Nishitani¹, Simon G Shepherd¹⁶, John Michael Ruohoniemi¹⁷ (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.Athabasca University, 1 University Drive, Athabasca, Alberta T9S 3A3, Canada, Department of Earth and Space Sciences, UCLA, Los Angeles, 90095, California, USA, 3.National Institute of Polar Research, Midori-cho 10-3, Tachikawa, Tokyo 190-8518, Japan, 4.Institute of Cosmophysical Research and Radiowave Propagation, Far Eastern Branch of the Russian Academy of Sciences, 5.Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, 6.NASA Goddard Space Flight Center, Greenbelt, MD, USA, 7.Los Alamos National Laboratory, Los Alamos, NM, USA, 8.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 9.Graduate School of Natural Science and Technology, Kanazawa University, 10.Graduate School of Science, Tohoku University, 11.Japan Aerospace Exploration Agency, 12.Department of Earth and Space Science, Graduate School of Science, Osaka University, 13.Academia Sinica Institute of Astronomy and Astrophysics, 14.Department of Earth and Planetary Science, School of Science, University of Tokyo, 15.Graduate School of Science, Tokyo University, 16.Thayer School of Engineering, Dartmouth College, Hanover, NH, USA, 17.Virginia Tech Department of Electrical and Computer Engineering, Blacksburg, VA, USA)

The subauroral latitudes around 60 degrees (MLAT: magnetic latitude) are the latitudes just below the auroral oval. This latitude range is connected, through the magnetic field lines, to a region in the inner magnetosphere where the outer boundary of the plasmasphere (plasmapause) and the inner boundary of the plasma sheet and ring-current particles are overlapped and produce unique auroras at these latitudes. In particular, Strong Thermal Emission Velocity Enhancement (STEVE) is a latitudinally-narrow, purple band of emission seen at subauroral latitudes, which was discovered in 2016. Further, well-known Stable Auroral Red (SAR) arcs also occurs at subauroral latitude. Red and green arcs, which are similar in that they occur in the subauroral latitudes to SAR arcs with only red emission, have been reported. However, comparing the characteristic of the magnetspheric plasma and electromagnetic field variations as a source of these three types of optical emissions have not been studied using conjugate observations between magnetospheric satellites and the ground-based imagers. In this study, we report the auroral characteristics deduced from all-sky image data obtained at seven locations at subauroral latitudes (Athabasca, Gakona, Husafell, Kapuskasing, Magadan, Nyrola and Tromsö) during about four years from January 2017 to April 2021. By calculating the ionospheric footprint of magnetospheric satellites (Arase and Van Allen Probes) onto the images with the Tsyganenko magnetic field model (TS04), we were able to identify four cases of STEVE, four cases of SAR arc, three cases of green and red arcs for which these satellites are at the source magnetosphere. For all three types of optical emissions, the plasmasphere and ring-current particles spatially overlap in the magnetospheric source region of the optical emission. An increase in the low-energy electron flux of the order of 0.1 to a few keV was also found for all types of arcs. Electromagnetic ion cyclotron (EMIC) waves were not associated with any of the events using Van Allen Probes satellites. The initial analysis of the SuperDARN radar data also showed a strong westward plasma flow in the ionosphere, especially during the STEVE events. These analyses not only provide the first comparison of the magnetospheric particle and electromagnetic field characteristics of the three types of optical emissions in the subauroral latitudes, but also provide an important summary of the differences and similarities between these optical emissions.