[P-EM08] 宇宙天気・宇宙気候

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

*村瀬 清華¹、片岡 龍峰^1,2、西山 尚典^1,2、西村 耕司^1,2,3、橋本 大志^1,2、田中 良昌^1,2,3、門倉 昭^1,2,3、冨川 喜弘^1,2、堤 雅基^1,2、内田 ヘルベルト陽仁¹、佐藤 薫⁴、笠原 慧⁴、三谷 烈史⁵、横田 勝一郎⁶、堀 智昭⁷、桂華 邦裕⁴、高島 健⁵、笠原 禎也⁸、松田 昇也⁵、小路 真史⁷、松岡 彩子⁹、篠原 育⁵、三好 由純⁷、佐藤 達彦¹⁰ (1.総合研究大学院大学、2.国立極地研究所、3.極域環境データサイエンスセンター、4.東京大学、5.宇宙科学研究所、6.大阪大学、7.名古屋大学、8.金沢大学、9.京都大学、10.日本原子力研究開発機構)

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.