Forward Cascade of Whistler Turbulence: Three-dimensional Particle-in-cell Simulations

Abstract

This manuscript describes the first ensemble of three-dimensional (3D) particle-in-cell (PIC) plasma simulations of whistler turbulence. The computational model represents a collisionless, homogeneous, magnetized plasma on which an initial spectrum of relatively long wavelength whistler fluctuations is imposed. The simulations represent a range of initial fluctuation amplitudes and follow the temporal evolution of the system as it decays into a broadband, anisotropic, turbulent spectrum at shorter wavelengths via a forward cascade. The resulting 3D turbulence is similar in many ways to whistler turbulence from previous two-dimensional (2D) PIC simulations, although the anisotropies in 3D are stronger than in comparable 2D runs. The most important difference is that reduced magnetic fluctuation spectra from the 3D simulations show a clear break in the perpendicular wavenumber (k ) spectra. Spectra at small k are relatively steep, but spectra at larger k are even steeper, similar in character to magnetic spectra at electron scales recently measured in the solar wind.