Source Altitudes and Heating Properties of Electron Conics Observed at High Altitudes by the Arase Satellite

Electron conics are a distinct electron distribution observed in Earth's magnetosphere, characterized by enhanced fluxes of upgoing electrons at several keV, especially in the auroral acceleration region. This study utilizes high-altitude (27,000-32,000 km) observations made by the Arase satellite to investigate the characteristics of electron conics after they have passed through the heating region, employing the high angular resolution of its Low-Energy Particle experiments - electron analyzer (LEPe). We analyzed eight electron conic events between 2017 and 2022 to estimate their source altitudes using mirror ratios and potential differences and by comparing pre- and post-heating data to investigate heating properties. Our results show that the source region of conics has an upper boundary at 9,000-14,000 km, with the peak flux originating from a central altitude of 3,000-7,000 km. This region spatially coincides with the source of auroral kilometric radiation (AKR): the the central altitude of the source of conics corresponds to the lower boundary of the AKR source, suggesting that a longer residence time of particles within the wave field lead to stronger heating. The analysis revealed that upgoing conic electrons exhibit higher temperatures and lower densities. While their number flux is conserved, indicating the energization of a magnetospheric population, the energy flux is enhanced by a factor of up to four, a rate higher than that reported in previous studies. A test particle simulation, using observed plasma parameters and incorporating stochastic perpendicular heating, reproduces the main features of observed conics in terms of both energy and pitch angle. Our simulation shows that electron conics evolve into narrow, field-aligned beams at higher altitudes, suggesting that some of the anti-Earthward-flowing beams observed in the magnetotail may actually be unresolved conics. These findings contribute to the understanding of energy transport between the auroral acceleration region and the magnetotail and show the importance of high-resolution instrumentation.