High sensitivity spectropolarimetric observations of the four Stokes
parameters of the solar Ca I 4227 Å line have been performed in
October 2010 at IRSOL with the ZIMPOL polarimeter, near the disk center,
outside an active region (Bianda et al. 2011). They were analyzed in Anusha
et al. 2011 with a combination of detailed radiative transfer modelling of
the Hanle effect for the linear
... [Show full abstract] polarization and weak field Zeeman
approximation for the circular polarization. This approach made possible a
unique determination of the magnetic field vector at various positions along
the slit of the spectrograph. A summary of the observations and of their
analysis is presented here.