日本地球惑星科学連合2018年大会

講演情報

[EE] ポスター発表

セッション記号 P (宇宙惑星科学) » P-EM 太陽地球系科学・宇宙電磁気学・宇宙環境

[P-EM16] Dynamics of Earth's Inner Magnetosphere and Initial Results from Arase

2018年5月22日(火) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:Danny Summers(Memorial University of Newfoundland)、三好 由純(名古屋大学宇宙地球環境研究所)、細川 敬祐(電気通信大学大学院情報理工学研究科、共同)、海老原 祐輔(京都大学生存圏研究所)

[PEM16-P03] Simulation of oblique propagation for whistler mode triggered emissions in a parabolic magnetic field

*野儀 武志1大村 善治1 (1.京都大学 生存圏研究所)

We perform two-dimensional electromagnetic particle simulation to study fundamental characteristics of whistler mode wave-particle interaction involved in chorus emissions propagating oblique to the background magnetic field. We assume simple periodic (x, y) system with the parabolic magnetic field taken in the x-direction. With the electrostatic components parallel to the magnetic field, which have been neglected in the previous simulation studies on chorus emissions, the distribution function in position can have a great influence on the simulation results. Assuming energetic electrons with anisotropic subtracted bi-Maxwellian velocity distribution function at the equator, we first put particles under harmonic bounce motion under a parabolic magnetic field. We next follow the motions of the particles adiabatically without any waves to obtain an equilibrium state as the initial distribution for
the particle simulation. It is necessary to put many super-particles in a grid cell to suppress the thermal fluctuation. With 30,000 particles per cell, we have confirmed a good agreement of the wave growth in the parallel direction with the linear growth rate. We next put an array of antennas with obliquely aligned to background magnetic field, and oscillate the antenna current with a variable frequency below the electron cyclotron frequency to excite a large amplitude whistler-mode wave obliquely propagating to the static magnetic field. In addition to the nonlinear trapping of energetic electrons through the cyclotron resonance, another nonlinear trapping of electrons by the Landau resonance takes place. Structures of the nonlinear trapping potentials changes with a varying frequency, affecting the efficiency of energy transfer between the wave and energetic electrons. We study nonlinear evolution of the wave packet, and competing processes of both resonances in accelerating the energetic electrons to higher energies.