Alfv\'en Wave Heating of the Solar Chromosphere: 1.5D models

TL;DR

This study uses high-resolution 1.5D non-ideal MHD models to investigate Alfvén wave heating of the solar chromosphere, highlighting the importance of shock heating over resistive dissipation.

Contribution

It demonstrates that shock heating from Alfvén waves dominates chromospheric heating, surpassing resistive dissipation, and clarifies the role of wave coupling and plasma compressibility.

Findings

Shock heating exceeds resistive dissipation in realistic models.

Ponderomotive coupling of Alfvén waves to sound waves is a key heating mechanism.

Hall term inclusion does not significantly affect heating rates.

Abstract

Physical processes which may lead to solar chromospheric heating are analyzed using high-resolution 1.5D non-ideal MHD modelling. We demonstrate that it is possible to heat the chromospheric plasma by direct resistive dissipation of high-frequency Alfv\'en waves through Pedersen resistivity. However this is unlikely to be sufficient to balance radiative and conductive losses unless unrealistic field strengths or photospheric velocities are used. The precise heating profile is determined by the input driving spectrum since in 1.5D there is no possibility of Alfv\'en wave turbulence. The inclusion of the Hall term does not affect the heating rates. If plasma compressibility is taken into account, shocks are produced through the ponderomotive coupling of Alfv\'en waves to slow modes and shock heating dominates the resistive dissipation. In 1.5D shock coalescence amplifies the effects of shocks and for compressible simulations with realistic driver spectra the heating rate exceeds that required to match radiative and conductive losses. Thus while the heating rates for these 1.5D simulations are an overestimate they do show that ponderomotive coupling of Alfv\'en waves to sound waves is more important in chromospheric heating than Pedersen dissipation through ion-neutral collisions.