Self Heating of Corona by Electrostatic Fields Driven by Sheared Flows

TL;DR

This paper proposes a mechanism for solar corona self-heating driven by electrostatic waves generated by sheared flows, which accelerate particles and increase plasma temperature through instabilities occurring throughout the corona.

Contribution

It introduces a novel self-heating mechanism involving sheared flow-driven electrostatic instabilities that operate universally in the corona, independent of density gradients.

Findings

Electrostatic potentials of about 100 volts can develop within seconds.

Instabilities occur across a range of perpendicular wavelengths from 1 to 10 meters.

Self-heating is significant due to pervasive sheared flow-driven electrostatic waves.

Abstract

A mechanism of self-heating of solar corona is pointed out. It is shown that the free energy available in the form of sheared flows gives rise to unstable electrostatic waves which accelerate the particles and heat them. The electrostatic perturbations take place through two processes (a) by purely growing sheared flow-driven instability and (b) by sheared flow-driven drift waves. These processes occur throughout the corona and hence the self-heating is very important in this plasma. These instabilities can give rise to local electrostatic potentials $\varphi$ of the order of about 100 volts or less within $3\times10^{-2}$ to a few seconds time if the initial perturbation is assumed to be about one percent that is $\frac{e\varphi}{T_{e}}\simeq10^{-2}$. The components of wave lengths in the direction perpendicular to external magnetic field $\textbf{B}_{0}$ vary from about 10m to 1m. The purely growing instability creates electrostatic fields by sheared flows even if the density gradient does not exist whereas the density gradient is crucial for the concurrence of drift wave instability. Subject headings: Sun: self-heating of corona, sheared flow-driven instability, drift waves.