[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-11] Do the EMIC waves really heat thermal ions in the plasmasphere?

*小路 真史¹、三好 由純¹、Lynn Kistler²、浅村 和史³、笠羽 康正⁴、松岡 彩子⁶、笠原 禎也⁵、松田 昇也⁵、土屋 史紀⁴、熊本 篤志⁴、中村 紗都子¹、Jun Chae-Woo¹、篠原 育³ (1.名古屋大学宇宙地球環境研究所、2.ニューハンプシャー大学、3.宇宙科学研究所、4.東北大学、5.金沢大学、6.京都大学)

キーワード：イオン加熱、EMIC波

Electromagnetic ion cyclotron (EMIC) waves are generated through the cyclotron wave-particle interaction, affecting the plasma environment in the magnetosphere. Heating of the ions by EMIC waves in the inner magnetosphere has also been investigated by spacecraft observations by comparing variations of ion distribution and waves. The energy transfer between the plasma waves and ions can be quantitatively evaluated by calculating the inner product between the wave electric field vector and the ion velocity vector, so-called WPIA (wave-particle interaction analysis). We adapt the WPIA method to the Arase spacecraft data and investigate the statistical results of the WPIA and the spatial distribution of the positive qV・E region in the inner magnetosphere. Using 4.5 years data, we choose EMIC wave events associating proton or helium flux enhancements of which the WPIA analysis can be applied for the necessary data sets observed by the Arase satellite. The energization of proton occurs over wide conditions, while the strongest energization of proton appears at K_p = 0 with the energy around 10 eV. On the other hand, the helium heating takes place at higher K_p>4 and with higher energy of the helium (>~ 100 eV). In the low K_p case, the energization of the helium is weak. In the magnetosphere, the occurrence peaks of the proton heating events appear in the dayside and post noon regions. In the higher K_p case, we find the occurrence peaks of heating of both proton and helium close to the Earth, around L=3-4 while in the smaller K_p case, the peaks appear around the noon and dusk side. Comparing the possible theoretical mechanisms of the ion flux enhancement, we conclude that the contribution of the EMIC heating to the warm plasma inside the plasmasphere is not significant.