Recent progress in astrophysical plasma turbulence from solar wind observations

TL;DR

This paper reviews recent advances in understanding solar wind plasma turbulence through spacecraft data, covering large-scale Alfvenic turbulence, compressive fluctuations, and small-scale kinetic turbulence, highlighting key findings and future directions.

Contribution

It provides a comprehensive overview of recent observational progress in solar wind turbulence, integrating models and measurements across scales.

Findings

Alfvenic turbulence dominates at large scales with critical balance and residual energy.

Compressive fluctuations constitute a few percent of energy and are related to Alfvenic components.

Kinetic range turbulence shows spectra and anisotropy consistent with cascade models.

Abstract

This paper summarises some of the recent progress that has been made in understanding astrophysical plasma turbulence in the solar wind, from in situ spacecraft observations. At large scales, where the turbulence is predominantly Alfvenic, measurements of critical balance, residual energy, and 3D structure are discussed, along with comparison to recent models of strong Alfvenic turbulence. At these scales, a few percent of the energy is also in compressive fluctuations, and their nature, anisotropy, and relation to the Alfvenic component is described. In the small scale kinetic range, below the ion gyroscale, the turbulence becomes predominantly kinetic Alfven in nature, and measurements of the spectra, anisotropy, and intermittency of this turbulence are discussed with respect to recent cascade models. One of the major remaining questions is how the turbulent energy is dissipated, and some recent work on this question, in addition to future space missions which will help to answer it, are briefly discussed.