[P-EM11] Dynamics of the Inner Magnetospheric System

[PEM11-P06] The characteristics of energetic protons in the energy of 10 eV-187 keV observed by the Arase satellite

*Chae-Woo Jun¹, Yoshizumi Miyoshi¹, Tomoaki Hori¹, Satoko Nakamura¹, Masahiro Kitahara¹, Masafumi Shoji¹, Sandeep Kumar¹, Lynn M Kistler^1,8, Chao Yue², Jacob Bortnik³, Larry Lyons³, Kazushi Asamura⁴, Shoichiro Yokota⁵, Satoshi Kasahara⁶, Kunihiro Keika⁶, Iku Shinohara⁴, Ayako Matsuoka⁷ (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.Institute of Space Physics and Applied Technology, Peking University, Beijing, China, 3.Atmospheric and Oceanic Sciences, University of California Los Angeles, Los Angeles, USA, 4.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan, 5.Osaka University, Osaka, Japan, 6.University of Tokyo, Tokyo, Japan, 7.Kyoto University, Kyoto, Japan, 8.University of New Hampshire, Durham, NH, USA)

Keywords:Energetic Proton distributions in the inner magnetosphere, 4 distinct proton populations within different energies, In-situ space observations obtained by the Arase satellite

Using the combined dataset of LEPi and MEPi data obtained by the Arase satellite from May 2017 to June 2021, we perform a statistical study of energetic protons (H+) in an extended energy range of 10 eV/q to 187 keV/q in the inner magnetosphere. In this study, we examined the H+ energy flux distributions and their pitch-angle distributions for different energies as a function of magnetic local time (MLT), magnetic latitude (MLAT), L shell, and geomagnetic activity based on Kp index. We find four distinct H+ populations within different energy ranges: (1) plasmaspheric H+ (E < 30 eV) at L < 5, (2) warm plasma cloak with pitch-angle distributions enhanced in the field-aligned direction at energies of several tens eV – several keV, (3) the ring current population (E = 1 keV – several tens of keV) with nose structures, (4) high-energy ring current particles (E > 30 keV) with symmetric distributions in MLT. These populations exhibit different behaviors as Kp increases. We also find the flux depletion region, called as ion dips, at E = 5-10 keV in the dawn sector at L=5-9 during Kp < 1. This region appears with a clear energy dependence on MLT from 0 to 21 MLT. We discuss the underlying physical dynamics for the different populations and compare the observational results with a model calculation using the simple electric and magnetic fields in UBK coordinates.