Whistler anisotropy instability: Spectral transfer in a three-dimensional particle-in-cell simulation

Abstract

A three-dimensional (3-D) particle-in-cell (PIC) simulation of the whistler anisotropy instability is carried out for a collisionless, homogeneous, magnetized plasma with βe=0.10. This is the first 3-D PIC simulation of the evolution of enchanced fluctuations from this growing mode driven by an anisotropic electron velocity distribution with T τe/T∥>1 where τ and ω represent directions perpendicular and parallel to the background magnetic field B o, respectively. The early-time magnetic fluctuation spectrum grows with properties reflecting the predictions of linear theory with narrowband maxima at kc/ωe≃ 1 and k×Bo=0, and a wave vector anisotropy in the sense of kτ<<kω. Here ωe represents the electron plasma frequency. At later times the fluctuations undergo both a forward transfer to shorter wavelengths, also with kτ<<kω, and an inverse transfer to longer wavelengths with wave vector anisotropy kτ>> kω. The inverse transfer is consistent with a prediction of nonlinear three-wave coupling theory. ©2014. The Authors.