Waves in the magnetized solar atmosphere. I. Basic processes and internetwork oscillations

We have modeled numerically the propagation of waves through magnetic structures in a stratified atmosphere. We first simulate the propagation of waves through a number of simple, exemplary field geometries in order to obtain a better insight into the effect of differing field structures on the wave speeds, amplitudes, polarizations, direction of propagation, etc., with a view to understanding the wide variety of wavelike and oscillatory processes observed in the solar atmosphere. As a particular example, we then apply the method to oscillations in the chromospheric network and internetwork. We find that in regions where the field is significantly inclined to the vertical, refraction by the rapidly increasing phase speed of the fast modes results in total internal reflection of the waves at a surface whose altitude is highly variable. We conjecture a relationship between this phenomenon and the observed spatiotemporal intermittancy of the oscillations. By contrast, in regions where the field is close to vertical, the waves continue to propagate upward, channeled along the field lines but otherwise largely unaffected by the field.