We simulate and study wave propagation in stellar atmospheres, in particular the atmosphere of the Sun. One of the problems to solve is the so called coronal heating problem. It relates to the question of why the temperature of the Sun’s corona is millions of kelvins higher than that of the surface.

TEMPERATURE AND DENSITY vary with height in the Sun's atmosphere, source <a href="http://history.nasa.gov/SP-402/p2.htm">NASA</a>
TEMPERATURE AND DENSITY in the Sun’s atmosphere, source NASA

Wave propagation is modeled by the equations of Magnetohydrodynamics (MHD), describing the dynamics of electrically conducting fluids, also known as plasmas. In addition a gravity source term is present, leading to interesting steady states.The waves are modeled as perturbations of these non-isothermal steady states of the system. In addition, due to the high temperatures, radiative transfer has to be included.

The equations are discretized by novel finite volume schemes for the induction equation, the ideal MHD equations and the M1 radiation MHD equations, see publications. These schemes are observed to be robust and resolve the complex physics well.

For more examples and animations see http://folk.uio.no/franzf.