A&A 385, 264-272 (2002)
Weak magnetic flux features on the SunB. Hartje and F. Kneer
Universitäts-Sternwarte, Geismarlandstraße 11, 37083 Göttingen, Germany
(Received 16 November 2001 / Accepted 15 January 2002 )
We observed weak magnetic flux in enhanced Ca K network and in its surroundings at various positions on the solar disc ( ). The Gregory Coudé Telescope at the Observatorio del Teide on Tenerife was used together with an image scanner and a Stokes V polarimeter. spectrograms in the 6302 Å region were taken. A second order flat fielding and smoothing brought the polarimetric sensitivity to a detection limit of 0.001 Ic (with Ic = continuum intensity) for exposure times of 300 ms in pixels corresponding to 0 0 19 ( slit width pixel size of detector). We present correlations between continuum intensity, line center intensity, and magnetic flux and discuss Stokes V profiles. The V amplitude asymmetry from areas with strong flux decreases towards the limb, a change of sign is not identified. The magnetic fields are ordered around strong flux centers with decreasing mean field strength outwards from the centers. In the range of Mx to Mx (in one pixel of cm 2) the probability distribution of the magnetic flux is ~ with , different from a Gaussian distribution. From this we derive tentativily a radial dependence from the flux centers of the form . For the probability distributions a significant center-to-limb variation is not detected. Together with the center-to-limb behaviour of the asymmetries, we interpret this tentatively as an isotropic orientation of the weak magnetic flux elements and of the gas flows. A vertical orientation of the magnetic fields is also compatible with the measurements, though.
Key words: Sun: photosphere -- magnetic fields -- techniques: polarimetric
Offprint request: F. Kneer, firstname.lastname@example.org
© ESO 2002