Parametric studies of ion and electron heating by whistler turbulence: three dimensional Particle-In-Cell simulations

Abstract:

Three-dimensional particle-in-cell simulations are utilized in order to model the forward cascade of an initially narrowband, isotropic spectrum of relatively long wavelength magnetosonic-whistler fluctuations in a collisionless, homogeneous, magnetized, electron-proton plasma. The intention of the investigation is to gain insight into the details of interaction between the electromagnetic fluctuations, the proton population, and the electron population. In particular, the manner in which each population is heated while the fluctuation energy dissipates is of interest. The results show that electrons are preferentially heated in the direction parallel to the background magnetic field, while ions are preferentially heated perpendicular to the background field. These behaviors appear to be universal with respect to the plasma β_e and the initial fluctuation amplitudes. In order to better understand how such heating scales at variable plasma parameters two parametric studies have been carried out. The first study holds β(t=0) fixed at β_e = β_i = 0.25, and varies the initial fluctuation energy density ε₀ = Σ δB²/B₀² = 0.025, 0.05, 0.1, 0.25, 0.5, while the second study holds ε₀(t=0) fixed at ε₀ = 0.1 and varies β_e = β_i = 0.05, 0.1, 0.25, 0.5, 1.0. The investigations show that the ion heating rates scale approximately linearly with ε₀, while they have a far weaker scaling with β_e.