[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P04] Statistical investigation of deformation of electron pitch angle distributions associated with chorus waves observed by Arase

*Tokuda Seiya¹, Takahiro Zushi¹, Satoshi Kurita², Hirotsugu Kojima², Satoshi Kasahara³, Shoichiro Yokota⁴, Yoshiya Kasahara⁵, Shoya Matsuda⁵, Satoko Nakamura⁶, Atsushi Kumamoto⁷, Fuminori Tsuchiya⁷, Ayako Matsuoka⁸, Yoshizumi Miyoshi⁶, Iku Shinohara⁹ (1.National Institute of Technology, Nara College , 2.Research institute for substainable humanosphere, Kyoto University, 3.The university of Tokyo, 4.Graduate School of Science, Osaka University, 5.Graduate School of Natural Science and Technology, Kanazawa University, 6.Institute for Space-Earth Enviromental Research, Nagoya University, 7.Graduate School of Science, Tohoku University, 8.Graduate School of Science, Kyoto University, 9.Japan Aerospace Exploration Agency / Institute of Space and Astronautical Science)

Keywords:Arase satellite, chorus wave, electron flux, resonance

In the Earth's inner magnetosphere, wave-particle interaction plays an important role in the acceleration and loss of energetic electrons. Kurita et al. (2018) reported a deformation of electron pitch angle distribution caused by the upper band chorus observed by the Arase satellite. In this event, it is shown that the deformation appears where effective wave-particle interaction is expected in the velocity space and the electron flux changes along the resonant ellipses. In this study, we analyzed the deformation of electron pitch angle distribution associated with chorus waves from the observation result of MEP-e and PWE onboard the Arase satellite in order to understand this phenomenon. We extracted events showing a sudden increase in electron flux in association with the activation of chorus waves from observation data of MEP-e and PWE. In the period from March 2017 to May 2018, 72 events were obtained. In this study, we calculated the resonant ellipses of the Cyclotron and Landau resonances in these events and attempted to analyze them by comparing them with the deformation of the electron pitch angle distribution. However, the UHR frequency could not be determined many times during the event and the plasma frequency was not available. In many events, electrostatic waves with a strong electric field component parallel to the magnetic field lines, which appear to be Langmuir waves, are observed simultaneously with the chorus wave. We calculated resonant ellipses using the Langmuir wave frequency as the plasma frequency in the 63 events where such waves were observed. As a result, 90% of events deformed along the resonant ellipses of the Cyclotron resonance.