||The Magnetic Configuration of a δ-Spot
||489, Solar Polarization 7
||Balthasar, H.; Beck, C.; Louis, R. E.; Verma, M.; Denker, C.
||Sunspots, which harbor both magnetic polarities within one
penumbra, are called δ-spots. They are often associated
with flares. Nevertheless, there are only very few
detailed observations of the spatially resolved magnetic field
configuration. We present an investigation performed
with the Tenerife Infrared Polarimeter at the Vacuum Tower
Telescope in Tenerife. We observed a sunspot with a main umbra
and several additional umbral cores, one of them with opposite magnetic
polarity (the δ-umbra).
The δ-spot is divided into two parts by a line along which
central emissions of the spectral line Ca II 854.2 nm appear.
The Evershed flow comming from the main umbra ends at this line.
In deep photospheric layers,
we find an almost vertical magnetic field for the δ-umbra,
and the magnetic field decreases rapidly with height, faster than
in the main umbra.
The horizontal magnetic field in the direction connecting main
and δ-umbra is rather smooth, but in one location next to a
bright penumbral feature at some distance to the δ-umbra, we
encounter a change of the magnetic azimuth by 90° from one
pixel to the next. Near the δ-umbra, but just outside,
we encounter a blue-shift of the spectral line profiles which we
interpret as Evershed flow away from the δ-umbra.
Significant electric current densities are observed at the dividing
line of the spot and inside the δ-umbra.