[P-EM10] Dynamics of Magnetosphere and Ionosphere

[PEM10-P05] The altitude distribution of electron conic source estimated with the Arase satellite

*石丸 宏樹¹、今城 峻²、三好 由純³、風間 洋一 ⁵、浅村 和史⁴、松岡 彩子²、Wang Shiang-Yu⁵、Tam Sunny⁶、Jun Chae-Woo³、堀 智昭³、篠原 育⁴ (1.京都大学、2.京都大学大学院理学研究科附属地磁気世界資料解析センター、3.名古屋大学宇宙地球環境研究所、4.宇宙航空研究開発機構宇宙科学研究本部、5.中央研究院、6.国立成功大学)

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 August and September 2017 and identified electron conics with ion beams observed at an altitude of ~30,000 km above the auroral acceleration region, on 31 August, 16 September and 28 September. 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 center and the upper edge of the electron conic source altitude were estimated to ~5000 km and ~10,000 km, respectively, from the determined mirror ratio. The source altitude distribution is consistent with the typical altitude of the auroral acceleration region, at which a large parallel electric field is formed. 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.