The extremely high-energy electron experiment (XEP) onboard the Arase (ERG) satellite

Nana Higashio,Iku Shinohara,Haruhisa Matsumoto,Takeshi Takashima

doi:10.1186/s40623-018-0901-x

Abstract

The extremely high-energy electron experiment (XEP) onboard the Arase (ERG) satellite is designed to measure high-energy electrons in the Earth’s radiation belts. The XEP was developed by taking advantage of our technical heritage of high-energy particle detectors that are onboard Earth observation satellites of the Japan Aerospace Exploration Agency (JAXA) as the radiation monitor. The main target of the XEP is to precisely measure variations of relativistic electrons in the outer radiation belt even during magnetic storms. The measurement is scientifically required to address physical mechanisms of electron acceleration and loss. The XEP consists of five solid-state silicon detectors (SSDs) and a single-crystal inorganic scintillator of cerium-doped gadolinium orthosilicate (GSO) to measure electrons in the energy range of 0.4–20 MeV and has a 20° single field of view (FOV). It is also equipped with a plastic scintillator that surrounds the GSO scintillator to prevent particles from entering the detectors from outside the FOV. The XEP has started its observation of relativistic electrons and has successfully observed dynamic variations of relativistic electron fluxes in the outer radiation belt during magnetic storms. This paper describes the instrumentation of the XEP and presents an example of initial observation results.

Highlights

Relativistic electrons are trapped in the Earth’s radiation belts, and the integrated flux of these electrons is known to vary widely during geomagnetic storms (e.g., Miyoshi and Kataoka 2005)
The electron energies detected in the scintillator region are determined only by signals in the scintillator region after the conditions are satisfied in the fieldprogrammable gate array (FPGA)
Summary The XEP is responsible for measuring the highest energy part of the whole energy range covered by four electron sensors onboard Arase, and it can precisely measure relativistic electrons up to 20 MeV to satisfy the mission requirements

Summary

Introduction

Relativistic electrons are trapped in the Earth’s radiation belts, and the integrated flux of these electrons is known to vary widely during geomagnetic storms (e.g., Miyoshi and Kataoka 2005). The results indicate that electrons up to ~ 5 MeV are stopped in the SSD region, and the XEP can observe these electrons (0.4–5 MeV) with the energy resolution of less than 8% at 0.4 MeV. The results show that electrons of 6–20 MeV are stopped in the SSD region and in the GSO scintillator region, and the XEP can observe these electrons (6–20 MeV) with the energy resolution less than 60% at 20 MeV.

Results

Conclusion