Perpendicular Ion Heating by Nonlinear Development of Finite Amplitude Whistler Wave

Abstract:

The solar wind consists of finite amplitude fluctuations which cause nonlinear turbulent cascade, instabilities, and plasma heating. The solar wind observations show that ion temperature perpendicular to the magnetic field is larger than the parallel temperature. Pitch angle scattering by ion cyclotron waves through wave-particle interactions could be an key role to describe the perpendicular heating of ions in the solar wind however, this study proposes another candidate.
We investigate nonlinear development of parallel propagating, ion-scale, finite amplitude whistler wave (parent wave), by using tow-dimensional, electromagnetic particle-in-cell simulations. Our simulation results show that Modified-Two-Stream Instability (MTSI), which comes from cross-field current of the parent wave, leads to fast dissipation of the wave compared with a time scale of decay instability. The MTSI generates quasi-perpendicular propagating whistler waves which scatter electrons and ions in the direction parallel and perpendicular to the background magnetic field, respectively. The wave generation and the scattering decrease the cross-field current, and causes the fast dissipation of the parent wave. The simulations suggest that the quasi-perpendicular propagating whistler waves have an important role to describe the perpendicular ion heating in the solar wind.