[P-EM13] 内部磁気圏

[PEM13-12] Instantaneous Frequency Analysis on Nonlinear EMIC Emissions: Arase Observation

*小路 真史¹、三好 由純¹、大村 善治²、Kistler Lynn^1,3、笠羽 康正⁴、松田 昇也⁵、笠原 禎也⁶、松岡 彩子⁵、野村 麗子⁷、石坂 圭吾⁸、熊本 篤志⁴、土屋 史紀⁴、八木谷 聡⁶、寺本 万里子¹、浅村 和史⁵、高島 健⁵、篠原 育⁵ (1.名古屋大学宇宙地球環境研究所、2.京都大学生存圏研究所、3.Institute for the Study of Earth Oceans and Space, University of New Hampshire、4.東北大学、5.宇宙科学研究所、6.金沢大学、7.国立天文台、8.富山県立大学)

キーワード：非線形波動粒子相互作用、あらせ衛星

In the inner magnetosphere, the Arase spacecraft has observed electromagnetic ion cyclotron (EMIC) emissions with both rising and falling frequencies. The instantaneous frequency analyses on the electromagnetic fields of the EMIC rising tone emission have been performed by the Hilbert-Huang transform. The time variation of the instantaneous frequency shows a good agreement with the nonlinear theory for the frequency evolutions. Rapid instantaneous frequency modulation is also found during the rising tone emission. We estimate the peak-to-peak time of the fluctuation in the frequency and find that the fluctuation is caused around a half of the particle trapping time. From the motion of the phase-bunched particle around the resonant velocity, it is expected that the nonlinear resonant current, which induces the falling frequency is formed in half the trapping time.