Development of Shear Alfven Mode Turbulence: Particle-In-Cell Simulations

Abstract:

In-situ observations show that solar wind plasmas are highly turbulent state. Frequency spectra in the solar wind plasmas observed at 1AU are very broad, ranging from a few mHz to tens of Hz. Fluctuations at low frequencies, which behave as magnetohydrodynamics (MHD) mode, are thought to cascade to those at high frequencies, ultimately resulting in plasma heating and acceleration due to the dissipation of fluctuations. Some kinetic wave mode, such as Alfven-cyclotron waves, kinetic Alfven waves, and whistler waves may contribute to the dissipation of fluctuations cascading from lower frequencies. However, an open question is that how the kinetic wave modes are generated from magnetohydrodynamic wave mode. The purpose of this study is to investigate the nonlinear development of shear Alfven mode turbulence which can be described in MHD approximation. Two-dimensional fully kinetic particle-in-cell simulation is used to demonstrate the shear Alfven mode cascades into kinetic-scale fluctuations which have wave-length smaller than ion inertial length. We will show that magnetic and plasma density fluctuations have different properties in wavenumber space, and discuss what kind of fluctuation becomes dominant at the kinetic scales.