Mechanical energy fluxes associated with saturated coronal heating in M dwarfs: comparison with predictions of a turbulent dynamo

TL;DR

This paper investigates the upper limits of coronal heating in M dwarfs by analyzing Alfven wave energy fluxes, linking magnetic field generation to observed X-ray luminosity saturation.

Contribution

It introduces a model connecting Alfven wave fluxes from stellar convection zones to coronal heating limits in M dwarfs, aligning theoretical predictions with observed X-ray saturation.

Findings

Alfven wave flux sets an upper limit on coronal heating.

The model explains the observed X-ray luminosity saturation.

Predicted flux limits match empirical data.

Abstract

Empirically, the X-ray luminosity LX from M dwarfs has been found to have an upper limit of about 0.2% of the bolometric flux Lbol. In the limit where magnetic fields in M dwarfs are generated in equipartition with convective motions, we use stellar models to calculate the energy flux of Alfven waves FA as a function of depth in the sub-surface convection zone. Since Alfven waves have the optimal opportunity for wave modes to reach the corona, we suggest that FA sets an upper limit on the mechanical flux Fmech which causes coronal heating. This suggestion accounts quantitatively for the saturated values of LX/Lbol which have been reported empirically for M dwarfs.