[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-03] Variations of He++ Ions in the inner magnetosphere at Different L-Shells: Arase LEP-i Observations

*西田 結衣¹、三好 由純¹、浅村 和史²、Lynn Kistler^1,3、篠原 育² (1.名古屋大学宇宙地球環境研究所、2.宇宙航空研究開発機構、3.ニューハンプシャー大学)

キーワード：あらせ衛星、内部磁気圏、アルファ粒子

He++ ions in the inner magnetosphere mainly originate from the solar wind and can s serve as tracers of solar wind-origin ions. However, due to the limited number of satellites that have continuously observed He++ ions in the inner magnetosphere, their detailed variations are still not well understood. The low-energy ion analyzer LEP-i onboard the Arase satellite has high mass resolution and can discriminate different ion groups, including He++. In this study, we analyzed Time-of-Flight (TOF) data from LEP-i with a 10-min time resolution to investigate the long-term variations of He++ ions in the inner magnetosphere and their dependence on L-shell. Our analysis covers the period from the declining phase of Solar Cycle 24 through the rising phase of Solar Cycle 25. The analysis of LEP-i/TOF observational data revealed that He++ ion counts exhibit different long-term variations in the outer region (L >= 4.5) and the inner region (L < 4.5), suggesting that the different loss time scale through charge-exchange. Furthermore, unlike previous studies based on the GEOS satellite, observations by the Arase satellite's LEP-i instrument suggest that He++ counts depend on both solar activity and geomagnetic activity.