PREPRINT
CC97E133-C9E7-40A0-A7AD-2DCA7811F9BB

Kinetic Turbulence in Collisionless High-Beta Plasmas

Lev Arzamasskiy, Matthew W. Kunz, Jonathan Squire, Eliot Quataert, Alexander A. Schekochihin
arXiv:2207.05189

Submitted on 11 July 2022

Abstract

We present results from three-dimensional hybrid-kinetic simulations of Alfv\'enic turbulence in a high-beta, collisionless plasma. The key feature of such turbulence is the interplay between local wave-wave interactions between the fluctuations in the cascade and the non-local wave-particle interactions associated with kinetic micro-instabilities driven by anisotropy in the thermal pressure (namely, firehose, mirror, and ion-cyclotron). We present theoretical estimates for, and calculate directly from the simulations, the effective collisionality and plasma viscosity in pressure-anisotropic high-beta turbulence, demonstrating that, for strong Alfv\'enic turbulence, the effective parallel viscous scale is comparable to the driving scale of the cascade. Most of the cascade energy (80-90%) is dissipated as ion heating through a combination of Landau damping and anisotropic viscous heating. The kinetic-energy spectrum of the turbulence has a slope steeper than 5/3 due to the anisotropic viscous stress. The magnetic-energy spectrum is shallower than 5/3 near the ion-Larmor scale due to fluctuations produced by the firehose instability. Our results have implications for models of particle heating in low-luminosity accretion onto supermassive black holes, the effective viscosity of the intracluster medium, and the interpretation of near-Earth solar-wind observations.

Preprint

Comment: 32 pages, 19 figures, submitted

Subjects: Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Solar and Stellar Astrophysics; Physics - Plasma Physics

URL: https://arxiv.org/abs/2207.05189