Time series of the observed line minimum position of Fe I 6301.5 Å. The characteristic evolution is shown for four sequences with different heliocentric position on the solar disk: (panel a) μ = 0.9 on the south axis (green rectangles), (panel b) μ = 0.8 on the north axis (blue circles), (panel c) μ = 0.5 on the east axis (orange diamonds), (panel d) μ = 0.3 on the west axis (red triangles). The wavelength scale (left y-axes in Å) is identical for all panels. The corresponding Doppler velocities (in m s⁻¹ ) can be identified by the right y-axes. The zero velocity is indicated by the dotted gray line.