Numerical simulations of wave propagation in the solar chromosphere .

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 modes at the layer of similar sound and Alfvén speeds, which we call the equipartition layer. At this layer 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.