Turbulence in the Solar Corona

TL;DR

This paper reviews observational and theoretical studies of turbulence in the solar corona, highlighting wave motions, ion heating, and the challenges of modeling multi-scale physical processes in this dynamic plasma environment.

Contribution

It synthesizes recent observational evidence and theoretical models to advance understanding of turbulence and wave interactions in the solar corona and solar wind.

Findings

Coronal turbulence involves wave motions across multiple scales.

Wave-particle interactions contribute to ion heating.

Modeling turbulence requires coupling processes across a wide range of spatial scales.

Abstract

The solar corona has been revealed in the past decade to be a highly dynamic nonequilibrium plasma environment. Both the loop-filled coronal base and the extended acceleration region of the solar wind appear to be strongly turbulent, but direct observational evidence for a cascade of fluctuation energy from large to small scales is lacking. In this paper I will review the observations of wavelike motions in the corona over a wide range of scales, as well as the macroscopic effects of wave-particle interactions such as preferential ion heating. I will also present a summary of recent theoretical modeling efforts that seem to explain the time-steady properties of the corona (and the fast and slow solar wind) in terms of an anisotropic MHD cascade driven by the partial reflection of low-frequency Alfven waves propagating along the superradially expanding solar magnetic field. Complete theoretical models are difficult to construct, though, because many of the proposed physical processes act on a multiplicity of spatial scales (from centimeters to solar radii) with feedback effects not yet well understood. This paper is thus a progress report on various attempts to couple these disparate scales.