[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

*Hyota Kaieda¹, Shoichiro Yokota¹, Kentaro Terada¹, Satoshi Kasahara², Kunihiro Keika², Tomoaki Hori³, Yoshizumi Miyoshi³, Iku Shinohara⁴ (1.The University of Osaka, 2.The university of Tokyo, 3.ISEE, Nagoya University, 4.ISAS/JAXA)

Keywords:Arase, ionosphere

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.