[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P01] Statistical Analysis of Proton Ring Distributions in the Inner Magnetosphere Using Arase Satellite

*Takahito Shikimori¹, Iku Shinohara², Kazushi Asamura³, Yoshizumi Miyoshi⁴, Shoichiro Yokota⁵, Satoshi Kasahara¹, Kunihiro Keika⁶, Tomoaki Hori⁴, Ayako Matsuoka⁷, Mariko Teramoto⁸, Kazuhiro Yamamoto⁴ (1.The University of Tokyo, 2.Japan Aerospace Exploration Agency/Institute of Space and Astronautical Science, 3.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 4.Institute for Space-Earth Environmental Research, Nagoya University, 5.Graduate School of Science, Osaka University, 6.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7.Data Analysis Center for Geomagnetism and Space Magnetism, Graduate School of Science, Kyoto University, 8.Kyushu Institute of Technology)

Keywords:Earth's magnetosphere, ring distribution, Magnetosonic wave

In recent years, wave-particle interactions in the inner magnetosphere have been found to play an important role. Since measuring plasma in the radiation belt is difficult, many studies have focused on plasma wave observations. However, there are fewer studies on the plasma that causes these waves, and many details of the wave excitation mechanism remain unclear.

Magnetosonic waves (MSWs), observed near the magnetic equator, are known to be excited by proton ring distributions (Liu et al., 2011). Recent studies also suggest that excited MSWs can further trigger electromagnetic ion cyclotron (EMIC) waves (Asamura et al., 2021), making them a topic of increasing interest. While many studies have observed MSWs in different events, detailed observations of the proton ring distributions that generate MSWs are still limited.


Statistical analysis using data from the Van Allen Probes has shown the spatial distribution of MSWs and proton ring distributions. However, these studies rely on one-dimensional data based on ring energy, and their results are not always consistent (Ma et al., 2013; Yuan et al., 2018; Zhou et al., 2021).

In this study, we use the LEP-i ion analyzer (30 eV–25 keV) onboard the Arase satellite to statistically analyze the three-dimensional velocity distribution of protons and check the proton ring distribution results from the Van Allen Probes (Yuan et al., 2018; Zhou et al., 2021). Previous studies used one-dimensional velocity data to confirm proton rings. In contrast, we use three-dimensional velocity data to better capture the structure of proton ring distributions (or shell distributions) and understand their statistical properties. Finally, we compare our results with those from the Van Allen Probes to study proton ring distributions in more detail.