The association between sunspot magnetic fields and superpenumbral fibrils
Louis, R.E.1,
Balthasar, H.1,
Kuckein, C.1,
Gömöry, P.2,
Puschmann, K.G.1,
Denker, C.1
1 Leibniz-Institut fur Astrophysik Potsdam, An der Sternwarte 16,
14482 Potsdam, Germany
2 Astronomical Institute of the Slovak Academy of Sciences,
05960 Tatranská Lomnica, Slovakia
Abstract:
Spectropolarimetric observations of a sunspot were carried out with the Tenerife Infrared Polarimeter at Observatorio del
Teide, Tenerife, Spain. Maps of the physical parameters were obtained from an inversion of the Stokes profiles observed
in the infrared Fe I line at 15 648 A. The regular sunspot consisted of a light bridge which separated the two umbral cores
of the same polarity. One of the arms of the light bridge formed an extension of a penumbral filament which comprised
weak and highly inclined magnetic fields. In addition, the Stokes V profiles in this filament had an opposite sign as the
sunspot and some resembled Stokes Q or U. This penumbral filament terminated abruptly into another at the edge of
the sunspot, where the latter was relatively vertical by about 30 degrees. Chromospheric Halpha and He II 304 A filtergrams
revealed three superpenumbral fibrils on the limb-side of the sunspot, in which one fibril extended into the sunspot and
was oriented along the highly inclined penumbral counterpart of the light bridge. An intense, elongated brightening was
observed along this fibril that was co-spatial with the intersecting penumbral filaments in the photosphere. Our results
suggest that the disruption in the sunspot magnetic field at the location of the light bridge could be the source of
reconnection that led to the intense chromospheric brightening and facilitated the supply of cool material in maintaining
the overlying superpenumbral fibrils.