[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P20] Statistical study of nonlinear EMIC wave-particle interaction on relativistic electrons in the magnetosphere observed by the Arase and Van Allen Probes

*Chae-Woo Jun¹、Yoshizumi Miyoshi¹、Tomoaki Hori¹、Khan-Hyuk Kim²、Jacob Bortnik³、Larry Lyons³、Takefumi Mitani⁴、Takeshi Takashima⁴、Iku Shinohara⁴、N. Higashio⁴、Ayako Matsuoka⁵、Yoshiya Kasahara⁶、Shoya Matsuda⁶、Yasumasa Kasaba⁷ (1.Institute for Space-Earth Environmental Research, Nagoya University、2.Kyung-Hee University, Suwon, Korea、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.Kyoto University, Kyoto, Japan、6.Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan、7.Graduate School of Science, Tohoku University, Sendai, Japan)

キーワード：EMIC rising-tone emissions with MeV electrons, In-situ observations using the Arase and Van Allen Probes, Wave-particle interaction in the inner magnetosphere

Electromagnetic ion cyclotron (EMIC) waves are known to play an important role in contributing to loss of relativistic (~ MeV) electrons in the outer radiation belts through pitch-angle scattering due to wave-particle interaction. Previous theoretical studies suggested that EMIC rising-tone emissions triggered by nonlinear wave growth can cause rapid losses of relativistic electrons in the inner magnetosphere. Our previous studies found the compressed dayside magnetosphere with the homogeneous magnetic field (dB/ds ~ 0) from the magnetic equator to higher magnetic latitudes provides a preferred condition for triggering nonlinear EMIC waves and these waves can interact with even sub-MeV electrons, leading to precipitation into the ionosphere. However, the influence of nonlinear EMIC wave-particle interactions on MeV electrons in the inner magnetosphere is not well understood yet. To clarify the relationship between nonlinear EMIC waves and MeV electrons in the magnetosphere, we perform a statistical study of relativistic electron variations associated with nonlinear EMIC waves using the Arase and Van Allen Probes. We select enhanced EMIC rising-tone emissions observed by either of the two missions from 2013 to 2023 for the recent solar cycle and classify the events into two categories: MeV flux variations associated with EMIC rising-tone emissions and weak relationships between them. Then, we investigate the characteristics (e.g., polarization sense, wave normal angle, Poynting vector, spatial distributions, solar activity, geomagnetic conditions, etc) of each category and compare them with each other. We discuss the underlying physical processes causing the loss of relativistic electrons in the outer radiation belt through EMIC wave-particle interactions.