Freiburg 2008 – wissenschaftliches Programm

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EP: Fachverband Extraterrestrische Physik

EP 4: The Sun and Heliosphere - Poster Session

EP 4.1: Poster

Montag, 3. März 2008, 17:30–19:00, Vorraum KGI-Aula

Observation of Sunspot Penumbrae with Hinode — •Morten Franz, Rolf Schlichenmaier, and Wolfgang Schmidt — Kiepenheuer Institut für Sonnenphysik, Freiburg, Germany

Sunspots appear in places where strong magnetic flux tubes penetrate the photosphere, thereby suppressing the convective energy transfer. This leads to a lower solar surface temperature, which will appear as a dark spot to the observer. Large spots consist of an umbra (dark center) and a penumbra (a semi-dark ring surrounding the umbra). Observations with resolution better than one arcsec reveal a substructure of the penumbra: an alternating pattern of bright and dark filaments extending outwards from the umbra into the quiet sun. These inhomogeneities are presumably caused by magnetic flux tubes that guide a constant flow of hot plasma towards the outer boundary of the penumbra. This flow is known and observed as the Evershed flow. Spectropolarimetric measurements, especially those of the net circular polarization (NCP) derived from the asymmetry of the Stokes V profile, provide information on the relation between gas flows and the magnetic field in the atmosphere of the penumbra. If a sunspot is examined at different positions on the solar disk, one may resolve the three-dimensional structure of the plasma flows and the magnetic fields. In this contribution, we present data from the spectropolarimeter of the Solar Optical Telescope onboard Hinode of a sunspot at different position on the solar disk. Furthermore, we explain how NCP and Doppler shift can be used to gain a deeper understanding of the topology of the plasma flow and the magnetic field in the penumbra of a sunspot.