Observed Stokes U/I_c profile (points) of Fig. 3 of Lagg et al. (2004) compared with the maximum U/I_c profiles computed for each height (solid line). At each height the observed and computed profile is plotted vs. λ. The same observed profile is repeated for comparison at each height. The computed Stokes I profile (not shown here) fits the observed intensity. The reference direction for positive Stokes Q forms an angle 12° with the nearest solar limb. This reference direction gives Q/I_c ≈ 0. The horizontal bar indicates the wavelength range, 10827.9–10831.6 Å  of the leftmost profile.