[P-EM10] Dynamics of Magnetosphere and Ionosphere

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

*Hiroki Ishimaru¹, Shun Imajo², Yoshizumi Miyoshi³, Yoichi Kazama⁵, Kazushi Asamura⁴, Ayako Matsuoka², Shiang-Yu Wang⁵, Sunny W. Y. Tam⁶, Chae-Woo Jun³, Tomoaki Hori³, Iku Shinohara⁴ (1.Kyoto University, 2.Data Analysis Center for Geomagnetism and Space Magnetism, Graduate School of Science, Kyoto University, 3.Institute for Space-Earth Environmental Research, Nagoya University, 4.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 5.Academia Sinica, 6.National Cheng Kung University)

Keywords:Electron conics, Auroral acceleration region

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.