JpGU-AGU Joint Meeting 2020

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P (Space and Planetary Sciences ) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM19] Dynamics of the Inner Magnetospheric System

convener:Kunihiro Keika(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo ), Aleksandr Y Ukhorskiy(Johns Hopkins University Applied Physics Laboratory), Yoshizumi Miyoshi(Institute for Space-Earth Environmental Research, Nagoya University), Lynn M Kistler(University of New Hampshire Main Campus)

[PEM19-P15] The observational study for high energy particles below L=2.1 using Hisaki

*Kazuo Yoshioka1, Ichiro Yoshikawa1, Atsushi Yamazaki2, Go Murakami2, Hajime Kita2, Fuminori Tsuchiya3, Tomoki Kimura4, Yoshizumi Miyoshi5, Satoshi Kurita5, Mariko Teramoto6 (1.Graduate School of frontier Science, The University of Tokyo, 2.Institute of Space and Astronautical Science / Japan Aerospace Exploration Agency, 3.Planetary Plasma and Atmospheric Research Center, Graduate School of Science, Tohoku University, 4.Tohoku University, 5.Institute for Space-Earth Environmental Research, Nagoya University, 6.Kyushu Institute of Technology)

Keywords:High energy particle, Hisaki, Low altitude

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.