Self-heating and its possible relationship to chromospheric heating in slowly rotating stars

TL;DR

This paper investigates how nonmodal instabilities in complex flows can amplify acoustic waves, leading to self-heating that may contribute to chromospheric heating in slowly rotating stars.

Contribution

It introduces a novel mechanism of nonmagnetic chromospheric heating via acoustic wave self-heating in inhomogeneous flows.

Findings

Nonmodal instabilities can significantly amplify acoustic waves.

Viscous dissipation converts wave energy into heat, contributing to flow heating.

Self-heating may be an additional mechanism for chromospheric heating in stars.

Abstract

The efficiency of nonmodal self-heating by acoustic wave perturbations is examined. Considering different kinds of kinematically complex velocity patterns we show that nonmodal instabilities arising in these inhomogeneous flows may lead to significant amplification of acoustic waves. Subsequently, the presence of viscous dissipation damps these amplified waves and causes the energy transfer back to the background flow in the form of heat; viz. closes the "self-heating" cycle and contributes to the net heating of the flow patterns and the chromospheric network as a whole. The acoustic self-heating depends only on the presence of kinematically complex flows and dissipation. It is argued that together with other mechanisms of nonlinear nature the self-heating \textit{may be} a probable additinal mechanism of nonmagnetic chromospheric heating in the Sun and other solar-type stars with slow rotation and extended convective regions.