Freiburg 2008 – wissenschaftliches Programm

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EP: Fachverband Extraterrestrische Physik

EP 7: The Sun and Heliosphere I

EP 7.5: Vortrag

Dienstag, 4. März 2008, 15:30–15:45, KGI-Aula

On the nature of coronal loops — •Sven Bingert, Pia Zacharias, and Hardi Peter — Kiepenheuer-Institut für Sonnenphysik, Freiburg

The structure and dynamics of a box in a stellar corona can be modeled employing a 3D MHD model for different levels of magnetic activity. Depending on the magnetic flux through the surface the nature of the resulting coronal structures can be quite different. We will compare two different models of an active region, one for two basically isolated sunspots, and another one for two sunspots surrounded by magnetic field patches comparable in magnetic flux to the sunspots.

Both models result in emission from the model corona being concentrated in loop structures. In the first case the loops seen in EUV and X-ray emission are following the magnetic field, following the general paradigm. However, in the second case, where the magnetic field is far from a force-free state, the loops seen in X-ray emission do not follow the magnetic field, but are more related to the current sheets formed in response to the footpoint motions of the magnetic field.

This result has serious implications for the interpretation of more complex magnetic structures, e.g. in the corona of active stars, where the majority of the emission might not come from loops following the magnetic field, indicating that loop-models might not be appropriate for more active coronae.