Linear polarization angle (upper panel) and total linear polarization fraction (middle panel) along the slit for the considered wavelength intervals (see text and Table 2). In the lower panel, the amplitude of the blue peak of the V/I signal in the Fe I 4224.2 Å line is shown as a function of the slit position. The values shown in all three panels are obtained from the data presented in Fig. 5. The error bars (statistical error) are reported in the upper left of each panel.