17:15 〜 19:15
[PEM13-P17] Wave damping of a chorus emission around half electron gyrofrequency under the stationary wave condition: result of 2D general curvilinear particle-in-cell simulation
キーワード：コーラス放射、2D PIC シミュレーション、ランダウ共鳴、非線形波動粒子相互作用
Whistler-mode chorus emissions are commonly observed in the Earth's inner magnetosphere, exhibiting a characteristic gap around 0.5 electron gyrofrequency (fce) in dynamic spectra. One proposed mechanism for this gap formation is nonlinear wave damping via Landau resonance, which occurs in oblique chorus wave-particle interactions. Chorus emissions are initially generated with a broadband frequency near the magnetic equator and subsequently experience damping at around 0.5 fce as they propagate toward higher latitudes. Observational evidence from the Geotail satellite [1], along with test-particle simulations [2], has supported this mechanism.
In this study, we employ a self-consistent two-dimensional general curvilinear particle-in-cell (2D gcPIC) simulation to investigate the nonlinear wave damping process. Our results successfully reproduce the formation of the spectral gap in slightly oblique chorus emissions. Through detailed analysis, we confirm that wave damping is accompanied by nonlinear interactions between chorus waves and energetic electrons via Landau resonance. we demonstrate that effective energy transfer from the wave to electrons occurs under a stationary wave condition, where the velocity parallel to the ambient magnetic field of a Landau resonant electron matches both the parallel wave phase velocity and the parallel wave group velocity. Furthermore, we conduct the relationship between wave normal angle of chorus emissions and wave frequencies under the stationary wave condition.
[1] Yagitani, S., T. Habagishi, and Y. Omura (2014), Geotail observation of upper band and lower band chorus elements in the outer magnetosphere, J. Geophys. Res. Space Physics, 119, doi:10.1002/2013JA019678.
[2] Hsieh, Y.-K., & Omura, Y. (2018). Nonlinear damping of oblique whistler mode waves via Landau resonance. Journal of Geophysical Research: Space Physics, 123. https://doi.org/10.1029/2018JA025848
In this study, we employ a self-consistent two-dimensional general curvilinear particle-in-cell (2D gcPIC) simulation to investigate the nonlinear wave damping process. Our results successfully reproduce the formation of the spectral gap in slightly oblique chorus emissions. Through detailed analysis, we confirm that wave damping is accompanied by nonlinear interactions between chorus waves and energetic electrons via Landau resonance. we demonstrate that effective energy transfer from the wave to electrons occurs under a stationary wave condition, where the velocity parallel to the ambient magnetic field of a Landau resonant electron matches both the parallel wave phase velocity and the parallel wave group velocity. Furthermore, we conduct the relationship between wave normal angle of chorus emissions and wave frequencies under the stationary wave condition.
[1] Yagitani, S., T. Habagishi, and Y. Omura (2014), Geotail observation of upper band and lower band chorus elements in the outer magnetosphere, J. Geophys. Res. Space Physics, 119, doi:10.1002/2013JA019678.
[2] Hsieh, Y.-K., & Omura, Y. (2018). Nonlinear damping of oblique whistler mode waves via Landau resonance. Journal of Geophysical Research: Space Physics, 123. https://doi.org/10.1029/2018JA025848