Observed (circles) and fitted Stokes profiles in two examples indicated in Fig. 1. Left panels: results corresponding to pixel indicated by plus (+) symbol. Right panels: results corresponding to pixel indicated by the square (▫). From top to bottom: intensity (Stokes I), linear polarization (Stokes Q and U), and circular polarization (Stokes V). Results after cycle 3 are indicated by the dashed red lines, whereas results after cycle 6 are shown as solid black lines.