[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-05] An analysis method to separate between N+ and O+ in the time-of-flight-mode data of MEP-i onboard the Arase satellite

*海江田 彪太¹、横田 勝一郎¹、寺田 健太郎¹、笠原 慧²、桂華 邦裕²、堀 智昭³、三好 由純³、篠原 育⁴ (1.大阪大学、2.東京大学、3.名古屋大学宇宙地球環境研究所、4.宇宙科学研究所/JAXA)

キーワード：あらせ、電離圏

The escape mechanism of the Earth's atmospheric ions still remains to be elucidated. Since heavy ions such as O+, N+, and molecular ions (N2+, NO+, and O2+) in the Earth’s magnetosphere originate only from the ionosphere, the observation of such ions may provide information on the atmospheric escape. For further understanding, therefore, it is important to investigate N+ as well as O+ and molecular ions. Since the N+/O+ ratio in the ionosphere varies with altitude and latitude, observations of N+ and O+ provide information on the altitude and latitude of atmospheric outflow(Liu et al, 2005). However, the mass-to-charge ratio of N+ and O+ are very close, making it difficult to separate them with ordinary spaceborne ion mass spectrometers. In order to evaluate the ion fluxes of all sorts of ions escaping from the Earth’s ionosphere to magnetosphere, we have developed an analysis method to separate N+, O+ and other sorts of ions in the time-of-flight (TOF)-mode data of the Medium-energy particle experiments Ion Mass Spectrometer(MEP-i) onboard the Arase satellite. We used the software “The Stopping and Range of Ions in Matter(SRIM)” to simulate the passage through the carbon foil of incident ions in the TOF chamber of MEP-i. We report on the details of the analysis method, and discuss heavy ion fluxes estimated by applying the method to the observation data of MEP-i.