Simulations and Modeling of Geospace Environment

摘要

We have conducted a series of test particle simulations of obliquely propagating whistler mode wave-particle interaction [1], showing that the perpendicular wave electric field can play a significant role in trapping and accelerating relativistic electrons through Landau resonance. A further theoretical and numerical investigation verifies that there occurs nonlinear wave trapping of relativistic electrons by the nonlinear Lorentz force of the perpendicular wave magnetic field. We have performed a subpacket analysis of chorus waveforms observed by the Van Allen Probes [2], and calculated the energy gain by the cyclotron acceleration through Landau resonance. We compare the efficiencies of accelerations by cyclotron and Landau resonances in typical events of rapid electron acceleration observed by the Van Allen Probes. By performing test particle simulations of relativistic electrons scattered by electromagnetic ion cyclotron (EMIC) rising tone emissions, we find a nonlinear scattering process namedSLPA (Scattering at Low Pitch Angle) totally different from the nonlinear wave trapping. The nonlinear wave trapping, occurring for high pitch angles away from the loss cone, scatters some of resonant electrons to lower pitch angles, and a fraction of the electrons is further transported into the loss cone by SLPA after being released from the wave trapping [3].