Whistler Turbulence Wavevector Anisotropies: Particle-in-cell Simulations

Abstract

Two-dimensional electromagnetic particle-in-cell simulations of whistler turbulence in a magnetized, homogeneous, collisionless plasma of electrons and protons are carried out. Enhanced magnetic fluctuation spectra are initially imposed at relatively long wavelengths, and, as in previous such simulations, the temporal evolution shows a forward cascade of magnetic fluctuation energy to shorter wavelengths, with more fluctuation energy at a given wavenumber perpendicular to B _o than at the same wavenumber parallel to the background field. The new result here is that the wavevector anisotropy is very different for each of the three components of the fluctuating magnetic field. Here, par denotes the direction parallel to the background magnetic field B _o , bottom indicates the direction perpendicular to B _o and in the simulation plane, and the symbol bottombottom denotes the direction perpendicular to both B _o and the simulation plane. The parallel magnetic fluctuations show more energy at k_{∥} than at k_{⊥}, whereas the perpendicular in-plane magnetic fluctuations show more energy at k_{⊥} than at k_{∥}. Finally, the out-of-plane magnetic fluctuations, |{δ}B_{⊥⊥}|^2, strongly prefer to propagate in the k_{⊥} direction.