Effects of electron drift on the collisionless damping of kinetic Alfv\'en waves in the solar wind

TL;DR

This paper investigates how electron drift influences the collisionless damping of kinetic Alfvén waves in the solar wind, revealing significant modifications to wave damping and energy partitioning in plasmas with drifting electron populations.

Contribution

It introduces a detailed analysis of kinetic Alfvén waves in plasmas with two drifting electron populations, highlighting the importance of electron drift effects on wave damping.

Findings

Electron drift significantly alters damping rates.

Proton-electron energy partition is affected by electron drift.

Electron drift must be considered in solar wind turbulence models.

Abstract

The collisionless dissipation of anisotropic Alfv\'enic turbulence is a promising candidate to solve the solar wind heating problem. Extensive studies examined the kinetic properties of Alfv\'en waves in simple Maxwellian or bi-Maxwellian plasmas. However, the observed electron velocity distribution functions in the solar wind are more complex. In this study, we analyze the properties of kinetic Alfv\'en waves in a plasma with two drifting electron populations. We numerically solve the linearized Maxwell-Vlasov equations and find that the damping rate and the proton-electron energy partition for kinetic Alfv\'en waves are significantly modified in such plasmas, compared to plasmas without electron drifts. We suggest that electron drift is an important factor to take into account when considering the dissipation of Alfv\'enic turbulence in the solar wind or other $\beta \sim 1$ astrophysical plasmas.