[P-EM10] Dynamics of Magnetosphere and Ionosphere

[PEM10-P17] The source altitude distribution and heating property of electron conic
estimated with the Arase satellite

*石丸 宏樹¹、今城 峻¹、三好 由純²、風間 洋一⁴、浅村 和史³、松岡 彩子¹、Shiang-Yu Wang⁴、Sunny Tam⁵、Jun Chae-Woo²、堀 智昭²、篠原 育³、土屋 史紀⁶、熊本 篤志⁶、笠原 禎也⁷ (1.京都大学大学院理学研究科、2.名古屋大学宇宙地球環境研究所、3.宇宙航空研究開発機構宇宙科学研究本部、4.中央研究院、5.国立成功大学、6.東北大学大学院理学研究科惑星プラズマ・大気研究センター 、7.金沢大学学術メディア創成センター)

キーワード：電子コニック、オーロラ加速領域

We examined the source altitude of electron conics by analyzing high-angular resolution electron data obtained by the Arase satellite. We surveyed electron conic events between 2017 and 2021 and identified electron conics with ion beams observed at an altitude of ~30,000 km above the auroral acceleration region. Assuming that the observed electron conics have adiabatically moved upward from the source altitude and undergone a potential difference along the dipole field line, we fit energy-dependent loss cone curves to the electron flux distribution of the conics to estimate the mirror ratio and the potential difference between the source and the satellite altitude. The electron conic source altitude approximately matched the simultaneously observed AKR source altitude, at which a parallel electric field is formed. In particular, the coincidence of the middle of the source altitude with the bottom altitude of the AKR suggests that heating is related to the time spent in the acceleration region. This result suggests two hypotheses for the generation of electron conics: electron heating due to time-varying electric fields that accelerate auroral electrons, and diffusive heating due to waves, such as electrostatic waves seen around this altitude. We also compared the phase space densities of downward and upward electrons to determine their heating property. We find that the number flux of upward and downward electrons are constant, while the energy fluxes vary widely, which implies that the magnetospheric electrons are heated.