Ion Heat and Parallel Momentum Transport by Stochastic Magnetic Fields and Turbulence

TL;DR

This paper develops a theory for how stochastic magnetic fields and turbulence cause ion heat and parallel momentum transport, highlighting the dominance of viscous stress over residual stress in typical conditions.

Contribution

It introduces a comprehensive theoretical framework for turbulent transport involving stochastic magnetic fields, emphasizing the viscous stress regime over the quasilinear residual stress.

Findings

Viscous stress dominates in practical parameter regimes.

Residual stress is not observable in typical conditions.

A simple physical model reproduces detailed analysis results.

Abstract

The theory of turbulent transport of parallel momentum and ion heat by the interaction of stochastic magnetic fields and turbulence is presented. Attention is focused on determining the kinetic stress and the compressive energy flux. A critical parameter is identified as the ratio of the turbulent scattering rate to the rate of parallel acoustic dispersion. For the parameter large, the kinetic stress takes the form of a viscous stress. For the parameter small, the quasilinear residual stress is recovered. In practice, the viscous stress is the relevant form, and the quasilinear limit is not observable. This is the principal prediction of this paper. A simple physical picture is developed and shown to recover the results of the detailed analysis.