Mode conversion of radiatively damped magnetogravity waves in the solar chromosphere

TL;DR

This study investigates how radiative damping affects the propagation and mode conversion of gravity waves in the solar chromosphere, extending previous adiabatic models to include damping effects.

Contribution

It introduces a model of radiatively damped gravity wave propagation in the solar atmosphere with inclined magnetic fields, revealing the persistence of mode conversion pathways under damping.

Findings

Mode conversion pathways are maintained with damping.

Wave energy fluxes are highly sensitive to radiative damping time.

Gravity waves are suppressed at the base of the photosphere with short damping times.

Abstract

Modelling of adiabatic gravity wave propagation in the solar atmosphere showed that mode conversion to field guided acoustic waves or Alfv\'en waves was possible in the presence of highly inclined magnetic fields. This work aims to extend the previous adiabatic study, exploring the consequences of radiative damping on the propagation and mode conversion of gravity waves in the solar atmosphere. We model gravity waves in a VAL-C atmosphere, subject to a uniform, and arbitrarily orientated magnetic field, using the Newton cooling approximation for radiatively damped propagation. The results indicate that the mode conversion pathways identified in the adiabatic study are maintained in the presence of damping. The wave energy fluxes are highly sensitive to the form of the height dependence of the radiative damping time. While simulations starting from 0.2 Mm result in modest flux attenuation compared to the adiabatic results, short damping times expected in the low photosphere effectively suppress gravity waves in simulations starting at the base of the photosphere. It is difficult to reconcile our results and observations of propagating gravity waves with significant energy flux at photospheric heights unless they are generated in situ, and even then, why they are observed to be propagating as low as 70 km where gravity waves should be radiatively overdamped.