Numerical simulations of wave propagation in the solar chromosphere

TL;DR

This paper uses 2D simulations to study wave interactions in the solar chromosphere, revealing how magnetic and acoustic waves exchange energy and behave near the equipartition layer, with implications for solar atmospheric dynamics.

Contribution

It introduces realistic, non-stationary 2D models of the solar atmosphere including radiative transfer, and analyzes wave mode interactions at the equipartition layer, highlighting magnetic wave refraction and mode conversion.

Findings

Fast magnetic mode is refracted back into the atmosphere.

Acoustic mode can be generated by internal or external sources.

Magnetic mode exhibits evanescent behavior in the chromosphere.

Abstract

We present two-dimensional simulations of wave propagation in a realistic, non-stationary model of the solar atmosphere. This model shows a granular velocity field and magnetic flux concentrations in the intergranular lanes similar to observed velocity and magnetic structures on the Sun and takes radiative transfer into account. We present three cases of magneto-acoustic wave propagation through the model atmosphere, where we focus on the interaction of different magneto-acoustic wave at the layer of similar sound and Alfv\'en speeds, which we call the equipartition layer. At this layer the acoustic and magnetic mode can exchange energy depending on the angle between the wave vector and the magnetic field vector. Our results show that above the equipartition layer and in all three cases the fast magnetic mode is refracted back into the solar atmosphere. Thus, the magnetic wave shows an evanescent behavior in the chromosphere. The acoustic mode, which travels along the magnetic field in the low plasma-$\beta$ regime, can be a direct consequence of an acoustic source within or outside the low-$\beta$ regime, or it can result from conversion of the magnetic mode, possibly from several such conversions when the wave travels across a series of equipartition layers.