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EP: Fachverband Extraterrestrische Physik

EP 8: Sonne

EP 8.1: Talk

Wednesday, March 28, 2007, 14:00–14:15, H46

The inhomogeneous magnetic field of a sunspot penumbra — •Rolf Schlichenmaier — Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, 79104 Freiburg.

A sunspot manifests the concentration of magnetic field in the solar photosphere. It consists of a central dark umbra which is surrounded by a brighter penumbral ring which reveals a radial filamentation on scales of 0.1 arcsec corresponding to some 100 km on the Sun. I will report on spectropolarimetric measurements of the magnetic field, which shows inhomogeneities that correspond to the radial filaments as seen in white light images. From these measurements the topology of the magnetic and velocity fields can be reproduced by modelling the radiative transfer of polarized light in the sunspot atmosphere. It is found that two magnetic field components with different inclinations and strengths co-exist in the penumbral atmosphere. The more inclined component is essentially horizontal and harbors a strong radial outflow, which is known as the Evershed flow. These findings have profound consequences for astrophysical magnetohydrodynamics as it sheds new light on our understanding of magnetoconvection in inclined magnetic fields.