Abstract
The Exploration of energization and Radiation in Geospace (ERG) project aims to study acceleration and loss mechanisms of relativistic electrons around the Earth. The Arase (ERG) satellite was launched on December 20, 2016, to explore in the heart of the Earth’s radiation belt. In the present paper, we introduce the specifications of the Plasma Wave Experiment (PWE) on board the Arase satellite. In the inner magnetosphere, plasma waves, such as the whistler-mode chorus, electromagnetic ion cyclotron wave, and magnetosonic wave, are expected to interact with particles over a wide energy range and contribute to high-energy particle loss and/or acceleration processes. Thermal plasma density is another key parameter because it controls the dispersion relation of plasma waves, which affects wave–particle interaction conditions and wave propagation characteristics. The DC electric field also plays an important role in controlling the global dynamics of the inner magnetosphere. The PWE, which consists of an orthogonal electric field sensor (WPT; wire probe antenna), a triaxial magnetic sensor (MSC; magnetic search coil), and receivers named electric field detector (EFD), waveform capture and onboard frequency analyzer (WFC/OFA), and high-frequency analyzer (HFA), was developed to measure the DC electric field and plasma waves in the inner magnetosphere. Using these sensors and receivers, the PWE covers a wide frequency range from DC to 10 MHz for electric fields and from a few Hz to 100 kHz for magnetic fields. We produce continuous ELF/VLF/HF range wave spectra and ELF range waveforms for 24 h each day. We also produce spectral matrices as continuous data for wave direction finding. In addition, we intermittently produce two types of waveform burst data, “chorus burst” and “EMIC burst.” We also input raw waveform data into the software-type wave–particle interaction analyzer (S-WPIA), which derives direct correlation between waves and particles. Finally, we introduce our PWE observation strategy and provide some initial results.
Highlights
In the Earth’s magnetosphere, various plasma phenomena simultaneously occur at various time, spatial, and energy scales
This study clarified that the whistler-mode chorus is primarily located near the inner edge of the outer radiation belt (L ~ 2.5) and gradually shifts outward (L ~ 4) with time and that the total wave energy generated during the storm is large enough to accelerate relativistic electrons
To select scientifically important and/or interesting events efficiently from the burst data, data selection is performed according to the following processes. (See numbered actions shown in Fig. 18.) As the continuous data are transmitted to the ground within 2 days after observation, (1) we hold an internet meeting once or twice a week to evaluate the continuous data, and (2) we select the burst data stored in the “read category” considering the available telemetry capacity assigned for the burst data
Summary
In the Earth’s magnetosphere, various plasma phenomena simultaneously occur at various time, spatial, and energy scales. When the output impedance K is much smaller than ZT, the effect of ZT is negligible and the calculated GWFC(f ) is equivalent to the end-to-end transfer function of the WPT-Pre (AC) and the WFC/ OFA(E) In this instance, the output impedance of 1 kΩ is used in the end-to-end calibration of the electric field waveform observation. Onboard data processing and data reduction As described in “PWE instrumentation” section, the electric and magnetic data measured by the WPT and MSC are fed into the EWO and HFA, processed by two CPU boards (CPU#8 and CPU#9) after analog-to-digital conversion, and sent to the satellite bus system as telemetry data. The OFA data are produced by a frequency analysis in the CPU boards, while the intermittent WFC data are output following digital signal processing: waveform compression for chorus mode or down-sampling for EMIC mode (Matsuda et al 2018). We organize timeline commands for the PWE according to the following:
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