Electric fields in solar magnetic structures due to gradient driven instabilities: heating and acceleration of particles

TL;DR

This paper investigates electrostatic instabilities caused by plasma gradients in solar magnetic structures, revealing their role in generating electric fields that accelerate particles and cause stochastic heating, potentially explaining coronal heating.

Contribution

It demonstrates that gradient-driven electrostatic instabilities can produce electric fields capable of accelerating particles and heating ions, with implications for solar corona heating.

Findings

Strongly growing modes exist for typical plasma parameters.

Electric fields from instabilities can accelerate particles in both directions.

Stochastic heating predominantly affects ions perpendicular to magnetic fields.

Abstract

The electrostatic instabilities driven by the gradients of the density, temperature and magnetic field, are discussed in their application to solar magnetic structures. Strongly growing modes are found for some typical plasma parameters. These instabilities i) imply the presence of electric fields that can accelerate the plasma particles in both perpendicular and parallel directions with respect to the magnetic field vector, and ii) can stochastically heat ions. The perpendicular acceleration is to the leading order determined by the $\bmath{E}\times \bmath{B}$-drift acting equally on both ions and electrons, while the parallel acceleration is most effective on electrons. The experimentally confirmed stochastic heating is shown to act mainly in the direction perpendicular to the magnetic field vector and acts stronger on heavier ions. The energy release rate and heating may exceed for several orders of magnitude the value accepted as necessary for a self-sustained heating in the solar corona. The energy source for both the acceleration and the heating is stored in the mentioned background gradients.