Evolution of plasma turbulence excited with particle beams

Lehrstuhl für Astronomie, Universität Würzburg, Emil-Fischer-Straße 31, 97074 Würzburg, Germany
e-mail: slange@astro.uni-wuerzburg.de

Received: 11 May 2012
Accepted: 4 September 2012

Abstract

Particles ejected from the Sun that stream through the surrounding plasma of the solar wind are causing instabilities. These generate wavemodes in a certain frequency range especially within shock regions, where particles are accelerated. The aim of this paper is to investigate of amplified Alfvénic wavemodes in driven incompressible magnetohydrodynamic turbulence. Results of different heliospheric scenarios from isotropic and anisotropic plasmas, as well as turbulence near the critical balance are shown. The energy transport of the amplified wavemode is governed by the mechanisms of diffusion, convection and dissipation of energy in wavenumber space. The strength of these effects varies with energy and wavenumber of the mode in question. Two-dimensional energy spectra of spherical k-space integration that permit detailed insight into the k_∥/k_⊥-development are presented. The evolution of energy injected through driving shows a strong energy transfer to perpendicular wavemodes. The main process at parallel wavemodes is the dissipation of energy in wavenumber space. The generation of higher harmonics along the k_∥ axis is observed. We find evidence for a critical balance in our simulations.