[P-PS06] 月の科学と探査

[PPS06-P25] Statistical study of low energy ions originated from the dayside of the Moon in the Earth’s magnetotail lobe

*Jaehee Lee¹、Khanhyuk Kim¹、Seulmin Baek²、Ho Jin¹、Jonghoon Lee¹、Ensang Lee¹、Yoshifumi Saito³、Masaki Nishino⁴、Shoichiro Yokota⁵ (1.Kyunghee Univ.、2.Korea Astronomy and Space Science Institute、3.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency、4.Tokyo University, Japan、5.Osaka University, Japan)

キーワード：Moon, magnetotail, Kaguya

Tanaka et al. (2009) reported that Moon-originating ions are generated by solar photon driven processes. However, there have been no statistical studies of Moon-originating ions. We have studied the statistical properties of low-energy ions originated from the dayside of the Moon using Kaguya data for 2008-2009 when the Moon was in the terrestrial magnetotail lobes. These lunar origin ions were detected in the energy range of 20~2000 eV observed at ~100 km altitude on the dayside. They mostly consist of heavy ions such as C⁺, O⁺, Na⁺, Al⁺, K⁺, and Ar⁺ and are distributed in a range of 50-130 degrees to the background magnetic field. In order to understand where and how Moon-originating ions are generated, we examine the relationship between energy and pitch angle and between energy and solar zenith angle. We found that the occurrence of the Moon-originating ions is high near Mare Nubium. To examine the observed energy and pitch angle of the lunar origin ions, test particle trajectory calculation is performed by assuming that the lunar origin ions detected at Kaguya orbit are energized by the electrostatic potential difference of 200 V between Kaguya and Moon. The particle calculation demonstrates that the initial speed of the ionized ions near the lunar surface plays a significant role in determining the observed pitch angle.