High-resolution studies of solar surface flows

Whereas in the interior of the sun all of the energy, which is generated by thermonuclear reactions in the center, is transported outwards by radiation, the transport is effected by flows (convection) in a spherical shell encomprising the outermost third of the solar body. Quite at the surface, where direct observations are feasible, this flow assumes the pattern of granulation, the subject of our project. Since the solar surface provides us with unique possibilities of studying astrophysical plasmas, great efforts are undertaken worldwide for its study. The present project intends to contribute to such investigations. It rests upon close cooperation between the groups in Graz (longstanding record of solar observations) and Vienna (modeling of convective flows). Especial emphasis will be laid upon detailed comparisons between observations and simulations. The Graz group will (in close cooperation with international partners and using the observational facilities of European solar physics) obtain new high-resolution observations. It will also perform the comparison with model calculations done in Vienna. We in Vienna will further develop our software which encomprises high-resolution numerics and our visualization system. As a result, we will be in the position to perform simulations which faithfully represent in particular the small spatial scales - which have been shown to possess so much fine structure by recent observations - and therefore to investigate these basic structures of the solar plasma closely. On the other hand, simulations will be run which refer to a larger portion of the surface and allow us to study collective effects of granules (mesogranulation, ) which are still poorly understood. Also for the work in Vienna external cooperations (Max Planck Institute for Astrophysics, D; National Center of Atmospheric Research, USA) will play an important role. Beyond the immediate results of the present project the software developed within it will allow later on to conduct similar studies for the stellar case, where by the very nature observations can by no means come close to what they accomplish for the sun and where therefore simulations will play a crucial role in providing detailed knowledge.

Whereas in the interior of the sun all of the energy, which is generated by thermonuclear reactions in the center, is transported outwards by radiation, the transport is effected by flows (convection) in a spherical shell encomprising the outermost third of the solar body. Quite at the surface, where direct observations are feasible, this flow assumes the pattern of granulation, the subject of our project. Since the solar surface provides us with unique possibilities of studying astrophysical plasmas, great efforts are undertaken worldwide for its study. The present project intends to contribute to such investigations. It rests upon close cooperation between the groups in Graz (longstanding record of solar observations) and Vienna (modeling of convective flows). Especial emphasis will be laid upon detailed comparisons between observations and simulations. The Graz group will (in close cooperation with international partners and using the observational facilities of European solar physics) obtain new high-resolution observations. It will also perform the comparison with model calculations done in Vienna. We in Vienna will further develop our software which encomprises high-resolution numerics and our visualization system. As a result, we will be in the position to perform simulations which faithfully represent in particular the small spatial scales - which have been shown to possess so much fine structure by recent observations - and therefore to investigate these basic structures of the solar plasma closely. On the other hand, simulations will be run which refer to a larger portion of the surface and allow us to study collective effects of granules (mesogranulation,...) which are still poorly understood. Also for the work in Vienna external cooperations (Max Planck Institute for Astrophysics, D; National Center of Atmospheric Research, USA) will play an important role. Beyond the immediate results of the present project the software developed within it will allow later on to conduct similar studies for the stellar case, where by the very nature observations can by no means come close to what they accomplish for the sun and where therefore simulations will play a crucial role in providing detailed knowledge.