[P-EM19] Dynamics of the Inner Magnetospheric System

[PEM19-P15] ひさき衛星を用いた低高度（L<2.1）における高エネルギー粒子の観測研究

*吉岡 和夫¹、吉川 一朗¹、山崎 敦²、村上 豪²、北 元²、土屋 史紀³、木村 智樹⁴、三好 由純⁵、栗田 怜⁵、寺本 万里子⁶ (1.東京大学大学院新領域創成科学研究科、2.宇宙航空研究開発機構宇宙科学研究所、3.東北大学大学院理学研究科惑星プラズマ・大気研究センター 、4.東北大学、5.名古屋大学宇宙地球環境研究所 、6.九州工業大学)

キーワード：高エネルギー粒子、ひさき衛星、低高度

Hisaki is a low-altitude satellite with an orbital altitude of about 1000 km and an inclination of 30 degrees which is equivalent to 1.2-2.1 in L-value. Hisaki has been designed as an EUV spectroscope for observing Jupiter and other planets, but its photon-detector is also sensitive to radiation such as protons and electrons. In particular, electrons of more than 5 MeV and protons of more than 50 MeV can penetrate the shield of the instrument and reach the detector. Therefore, Hisaki can be used as a radiation monitor in the low altitude area (low L-value).

The Hisaki launched in November 2013 has been observing planets for more than 6 years. We have summarized the count rates caused by radiation and clarified that the trend is dependent on solar activity in orbital regions with L-values greater than 1.8. In addition, it was confirmed that the count increased several times with a timescale of several hours in response to solar activity like SEP. These phenomena were also captured by radiation monitors onboard the ISS in the orbital region of higher L-values (L>3) and were recognized as SEP particle injection. However, no clear observational evidence has been obtained for the behavior near L-value 2.

In this presentation, we will discuss the behavior of high-energy particle at various time constants in the low-altitude region around Earth.