Parallel electric field amplification by phase-mixing of Alfven waves

TL;DR

This paper investigates how phase mixing of Alfven waves in collisionless plasmas amplifies parallel electric fields, leading to electron acceleration and energy transfer, using drift-kinetic theory to analyze wave damping and evolution.

Contribution

It provides a theoretical framework for understanding parallel electric field amplification via phase mixing in collisionless plasmas, emphasizing electron Landau damping effects.

Findings

Parallel electric field amplification occurs through phase mixing in collisionless plasmas.

Electron Landau damping is the dominant energy dissipation mechanism.

Maximum electric field amplification and relevant scales are quantitatively evaluated.

Abstract

Previous numerical studies have identified "phase mixing" of low-frequency Alfven waves as a mean of parallel electric field amplification and acceleration of electrons in a collisionless plasma. Theoretical explanations are given of how this produces an amplification of the parallel electric field, and as a consequence, also leads to enhanced collisionless damping of the wave by energy transfer to the electrons. Our results are based on the properties of the Alfven waves in a warm plasma which are obtained from drift-kinetic theory, in particular, the rate of their electron Landau damping. Phase mixing in a collisionless low-$\beta$ plasma proceeds in a manner very similar to the visco-resistive case, except for the fact that electron Landau damping is the primary energy dissipation channel. The time and length scales involved are evaluated. We also focus on the evolution of the parallel electric field and calculate its maximum value in the course of its amplification.