[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

*栗田 怜¹、江田 大輝¹、小嶋 浩嗣¹、風間 洋一²、笠原 禎也³、松田 昇也³、松岡 彩子⁴、Wang Shiang-Yu²、Jun Chae-Woo⁵、中村 紗都子⁵、三好 由純⁵、篠原 育⁶ (1.京都大学生存圏研究所、2.台湾中央院天文及天文物理研究所、3.金沢大学、4.京都大学、5.名古屋大学宇宙地球環境研究所、6.宇宙科学研究所)

キーワード：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.