Parallel electric field generation by Alfven wave turbulence

TL;DR

This paper investigates how anisotropic Alfvenic turbulence generates parallel electric fields, which are crucial for electron acceleration in solar flare plasmas, by deriving scaling relations and a spectrum for these electric fields.

Contribution

It introduces a reduced two-fluid plasma model for anisotropic Alfvenic turbulence and derives the spectrum of parallel electric field fluctuations relevant for electron acceleration.

Findings

Parallel electric fields develop at large MHD scales due to turbulence.

Derived spectrum can model electron acceleration in solar flares.

Scaling relations link electromagnetic fluctuations to turbulence scales.

Abstract

{This work aims to investigate the spectral structure of the parallel electric field generated by strong anisotropic and balanced Alfvenic turbulence in relation with the problem of electron acceleration from the thermal population in solar flare plasma conditions.} {We consider anisotropic Alfvenic fluctuations in the presence of a strong background magnetic field. Exploiting this anisotropy, a set of reduced equations governing non-linear, two-fluid plasma dynamics is derived. The low-$\beta$ limit of this model is used to follow the turbulent cascade of the energy resulting from the non-linear interaction between kinetic Alfven waves, from the large magnetohydrodynamics (MHD) scales with $k_{\perp}\rho_{s}\ll 1$ down to the small "kinetic" scales with $k_{\perp}\rho_{s} \gg 1$, $\rho_{s}$ being the ion sound gyroradius.} {Scaling relations are obtained for the magnitude of the turbulent electromagnetic fluctuations, as a function of $k_{\perp}$ and $k_{\parallel}$, showing that the electric field develops a component parallel to the magnetic field at large MHD scales.} {The spectrum we derive for the parallel electric field fluctuations can be effectively used to model stochastic resonant acceleration and heating of electrons by Alfven waves in solar flare plasma conditions}