[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-P32] On the formation of plateau in electron distribution function associated with chorus-related electrostatic waves observed by the Arase satellite

*Satoshi Kurita¹, Daiki Eda¹, Hirotsugu Kojima¹, Yoichi Kazama², Yoshiya Kasahara³, Shoya Matsuda³, Ayako Matsuoka⁴, Shiang-Yu Wang², Chae-Woo Jun⁵, Satoko Nakamura⁵, Yoshizumi Miyoshi⁵, Iku Shinohara⁶ (1.Research Institute for Sustainable Humanosphere, Kyoto University, 2.Institute of Astronomy and Astrophysics, Academia Sinica, 3.Kanazawa University, 4.Kyoto University, 5.ISEE, Nagoya University, 6.ISAS/JAXA)

Keywords:chorus, electrostatic waves, Arase satellite

Whistler mode chorus waves are electromagnetic waves in nature and typically observed in the frequency range from 0.1 to 0.8 times of electron gyrofrequency in the magnetosphere. The waves are known to play crucial roles in the dynamics of the magnetosphere through resonant wave-particle interactions. Previous studies report on the observation of electrostatic waves related to the appearance of chorus waves [Reinleitner et al., 1983, Li et al., 2017]. The electrostatic waves have electric field oscillation parallel to the ambient magnetic field and are considered to be excited by electron beams generated by Landau resonance between electrons and chorus waves. It is suggested that the narrow-band electrostatic waves correspond to the Langmuir waves [Li et al., 2017]. The signature of electron beams is also reported from the observation of a plateau in the electron distribution function parallel to the ambient magnetic field [Reinleitner et al., 1983, Li et al., 2017]. The question raised here is how the plateau is formed through the interaction between electrons and the waves since both the electrostatic waves and chorus can be candidates to create the plateau through the Landau resonance. We quantitatively evaluate the cause of the plateau formation in the electron distribution functions considering the trapping velocity of electrons in the electrostatic potential of the electrostatic waves and the chorus waves based on the Arase satellite observation. The effect of the propagation of chorus waves from the magnetic equator to higher latitudes is also considered. In the presentation, we will discuss the possible cause of the plateau observed by the Arase satellite by explaining the observed plateau energy range.