Modeling ULF Waves in the Inner Magnetosphere-A Comparison between Hybrid Simulations and a Full Wave Finite Element Model

Previous theoretical and observational studies have indicated that EMIC wave perturbations play an important role in the loss of radiation belt particles in the inner magnetosphere. Because the wave-particle interactions depend sensitively on wave amplitude and polarization, it is important to accurately model the wave mode structures. In this presentation, we explore two methods to describe these waves: simulations with a 3D hybrid code in dipole geometry (GCPIC-hybrid) and a full wave finite element code, PETRA-M, that has been adapted to space plasmas. The intention is to verify performance for the two simulation methods for small wave amplitudes in the linear regime, and to identify nonlinear effects based on differences in the nonlinear regime. We consider EMIC wave generation and propagation in a dipole magnetosphere including the effect of heavy ions. For the hybrid simulations, waves are generated near the equator due to anisotropy and propagate to higher latitude. For comparison, the spectrum of waves generated in the hybrid simulation is launched in the full wave simulation code. We compare the wave mode structures, Poynting flux, and polarization of the two codes and discuss similarities and differences. Implications for radiation belt loss processes are discussed.