[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P28] 脈動オーロラに伴う高エネルギー電子の中層大気への降りこみ：あらせ衛星とEISCATの共同観測

*尾林 佑哉¹、三好 由純¹、高橋 一輝¹、細川 敬祐²、小川 泰信³、齋藤 慎司⁴、大山 伸一郎¹、浅村 和史⁵、風間 洋一⁶、Wang Shiang-Yu⁶、笠原 慧⁷、横田 勝一郎⁸、三谷 烈史⁵、高島 健⁵、篠原 育⁵、Jun Chae-Woo¹、堀 智昭¹、桂華 邦裕⁷、笠原 禎也⁹、松田 昇也⁹、土屋 史紀¹⁰、熊本 篤志¹⁰、中村 紗都子¹、松岡 彩子¹¹、Antti Kero¹²、Verronen Pekka^12,13、Turunen Esa¹² (1.名古屋大学宇宙地球環境研究所、2.電気通信大学、3.国立極地研究所、4.情報通信研究機構、5.宇宙航空研究開発機構、6.Academia Sinica, Taiwan、7.東京大学、8.大阪大学、9.金沢大学、10.東北大学、11.京都大学、12.Sodankyla Geophysical Observatory, Finland、13.Finnish Meteorological Institute, Helsinki, Finland)

キーワード：あらせ衛星、EISCAT、脈動オーロラ

Wave-particle interactions with lower band whistler-mode chorus waves (LBC) near the equator result in electron precipitation with energies ranging from 1-100 keV, leading to the pulsating aurora (PsA). Recent studies have shown that sub-relativistic/relativistic electrons with energies of several hundred of keV to several MeV are scattered by chorus waves that propagates to high latitudes along the field line, and these electrons precipitate into the mesosphere at an altitude of 60-80 km simultaneously with PsA (Miyoshi et al., 2015, 2020, 2021). We investigate high-energy electron precipitation during PsA events at Tromsø, Norway, from 02:00 to 06:00 UT on March 12, 2022, using data from the Arase satellite and the EISCAT radar. We estimate the electron energy spectrum from EISCAT observations. The analysis confirmed that electron precipitation occurred in wide energy range, and particularly strong precipitation was observed at energies of several tens of keV, and the estimated maximum energy of the precipitating electrons is ~300 keV. We then derived the pitch angle diffusion coefficient of electrons through chorus wave particle interactions using the Arase/PWE OFA data. Our result indicates that the estimated life time from a quasi-linear theory is comparable to the theoretical strong diffusion limit, implying that the observed plasma waves in the magnetosphere drive strong precipitation observed by the EISCAT radar. Moreover, our analysis confirms that chorus waves propagate to the higher latitudes can resonate more energetic electrons as shown in the estimation of the pitch angle diffusion coefficient. Considering these analyses, we conclude that the pitch angle scattering by LBC along the field line leads to wide energy electron precipitation from a few keV to more than 100 keV during PsA, as observed by the EISCAT radar.