[P-EM08] Space Weather and Space Climate

[PEM08-09] Energetic electron precipitation events as identified in the mesosphere during substorms

*Kiyoka Murase¹, Ryuho Kataoka^1,2, Takanori Nishiyama^1,2, Koji Nishimura^1,2,3, Taishi Hashimoto^1,2, Yoshimasa Tanaka^1,2,3, Akira Kadokura^1,2,3, Yoshihiro Tomikawa^1,2, Masaki Tsutsumi^1,2, Herbert Akihito Uchida¹, Kaoru Sato⁴, Satoshi Kasahara⁴, Takefumi Mitani⁵, Shoichiro Yokota⁶, Tomoaki Hori⁷, Kunihiro Keika⁴, Takeshi Takashima⁵, Yoshiya Kasahara⁸, Shoya Matsuda⁵, Masafumi Shoji⁷, Ayako Matsuoka⁹, Iku Shinohara⁵, Yoshizumi Miyoshi⁷, Tatsuhiko Sato¹⁰ (1.The Graduate University for Advanced Studies, 2.National Institute of Polar Research, 3.Polar Environment Data Science Center, 4.The University of Tokyo, 5.Institute of Space and Astronautical Science, 6.Osaka University, 7.Nagoya University, 8.Kanazawa University, 9.Kyoto University, 10.Japan Atomic Energy Agency)

Auroral activities have significant impacts on the polar atmosphere. One of the important aspects is the energy deposition to the neutral atmosphere by the precipitation of energetic electrons, which is known as a possible cause of the mesospheric ozone depletion. Energetic electron precipitation (EEP) will provide clues to the understanding of the links between the space and the atmospheric environment via energetic particles. We report EEP events during substorms, in which conjugate observations were conducted between Syowa Station in the Antarctic region and the Arase satellite in the magnetosphere. First, the mesospheric ionization reaching at 70 km altitude was identified during the growth phase. The mechanism of the growth phase EEP event was presumed to be the current sheet scattering because of the observed latitudinal energy dispersion of precipitating electrons, as identified from the all-sky imager and imaging riometer. During the expansion phase, the Arase satellite detected the increase of the loss-cone electron flux with the initiation of whistler mode waves. The estimated atmospheric ionization level due to the loss-cone electrons was consistent with the observed amplitude of the cosmic noise absorption. During the recovery phase, long-lasting enhanced activities of whistler mode waves were observed with the pulsating aurora. These results indicate that the current sheet scattering plays an essential role to cause EEP events during the growth phase, while the wave-particle interaction plays an essential role after the substorm onset.