[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P15] Multi-event analysis of penetration of plasmasheet electrons into the plasmasphere using the Arase satellite

*Masaki Gomi¹, Kazuo Shiokawa¹, Yoshizumi Miyoshi¹, Yuichi Otsuka¹, Shin-ichiro Oyama¹, Atsuki Shinbori¹, Tomoaki Hori¹, Chae-Woo Jun¹, Kazuhiro Yamamoto¹, Iku Shinohara², Kazushi Asamura², Satoshi Kasahara³, Kunihiro Keika³, Shoichiro Yokota⁴, Fuminori Tsuchiya⁵, Atsushi Kumamoto⁵, Yoshiya Kasahara⁶, Yoichi Kazama⁷, Shiang-Yu Wang⁷, Tam Sunny W.Y⁸, Ayako Matsuoka⁹, Connors Martin¹⁰ (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.Japan Aerospace Exploration Agency, 3.Tokyo University, 4.Osaka University, 5.Tohoku University, 6.Kanazawa University, 7.Academia Sinica Institute of Astronomy and Astrophisics, 8.National Cheng Kung University, 9.Kyoto University, 10.Athabasca University)

Some auroras are known to extend to latitudes lower than the aurora oval, such as discrete auroras of STEVE and SAR arcs, and diffuse auroras of Evening Corotating Patches (ECP, Kubota et al., GRL, 2003). However, direct observation of the magnetospheric source region of diffuse low-latitude emission has not been performed so far.
In our studies so far, we used the Arase satellite and three all-sky cameras at Kapuskasing (magnetic latitude: 59.0N, geographic latitude and longitude: 49.4N, 277.8E) and Athabasca (magnetic latitude: 62.5N, geographic latitude and longitude: 54.6N, 246.4E) in Canada and Gakona (magnetic latitude: 63.6N, geographic latitude and longitude: 62.4N, 214,8E) in Alaska. We reported two conjugate observation events in the magnetospheric source region of diffuse emission extending to latitudes lower than the auroral oval. In these two events, common characteristics were found that the low-latitude boundary of the auroral oval coincided with one of the boundaries of the plasmasheet particles and was located near the plasmapause. The source region of the diffuse emission region corresponded to the ~0.1-20 keV plasmasheet electron population in the plasmasphere, which was located inward of the low-latitude boundary of the plasmasheet. These electrons have a larger flux in the perpendicular direction than in the field-aligned direction, presumably because long after the injection of plasma sheet electrons from the magnetotail into the inner magnetosphere, the field-aligned electrons were lost as they precipitated into the atmosphere.
In addition to these analyses, we remove the limitation of simultaneous observations with the ground to increase the number of cases where plasmasheet electrons are observed in the plasmasphere by the Arase satellite. This multi-event analysis provides further insight into the mechanism of plasmasheet electron penetration into the plasmasphere.