The Three-dimensional Structure of Sunspots

Several active regions were observed simultaneously with the solar telescopes on Tenrife, VTT and THEMIS in May and June 2005. At both telescopes, spatial scans across sunspots were performed. At the VTT, a group of iron and silicon lines in the near infrared were used, at THEMIS we obtained data in photospheric iron and chromium lines simultaneously with Na_D1 and H_alpha. For all lines the full Stokes-vector was recorded. The magnetic field strength, its inclination and azimuth as well as the Doppler velocity were derived from inversions carried out independently for the different lines.

From the data reduced so far we find the following results: The magnetic field strength decreases with height in the penumbra, and the magnetic field is less inclined in higher layers. We encounter locations where the vertical component of the magnetic field increases with height. Penumbral Doppler velocities (Evershed effect) are higher in deeper layers.
Outside spots and other dark photospheric features, the magnetic field strength increases, in agreement with the assumption of canopies in layers above 300 km.