Lifetime of Relativistic Electrons in the Radiation Belt observed with the HEP Instruments onboard Arase

Thursday, 8 March 2018
Lakehouse (Hotel Quinta da Marinha)
Takefumi Mitani1, Yoshizumi Miyoshi2, Inchun Park Mr.2, Tomoaki Hori3, Nana Higashio4, Satoshi Kasahara5, Takeshi Takashima5 and Iku Shinohara6, (1)ISAS/JAXA, Kanagawa, Japan, (2)Nagoya University, Nagoya, Japan, (3)Nagoya Univ. STE lab., Nagoya, Aichi, Japan, (4)JAXA, Tukuba, Japan, (5)ISAS Institute of Space and Astronautical Science, Kanagawa, Japan, (6)ISAS/JAXA, Sagamihara, Japan
Abstract:
The ERG/Arase spacecraft was successfully launched on December 20, 2016. After the commissioning phase, nine science instruments have started thier observation since late March, 2017. “High energy Electron exPeriment (HEP)” onboard the Arase satellite observes 70 keV - 2 MeV electrons and provides a 3-D velocity distribution function every spacecraft spin period. HEP is composed of two types of telescopes, HEP-L and HEP-H. HEP-L observes 0.1 - 1 MeV electrons and its geometrical factor is about 10-3 cm2 str, and HEP-H observes 0.7 - 2 MeV and G-factor is about 10-2 cm2 str.

Since HEP started its normal observations, it has observed several cycles of sudden depletion and recovery of electron fluxes in the outer radiation belt in response to geomagnetic storms. When the geomagnetic activity was low for about a month, the electron fluxes slowly decrease in the outer radiation belt.

We present the initial results of the HEP observations for about 10 months. We espescially focus on the lifetime of relativistic electrons in the outer radiation belts when the geomagnetic avtivity is low.

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