Time slices of movies mv07 (left column) and mv08 (right column) showing the apparent motions of structures seen in the normalised intensity I_out/I_ph, magnetic inclination γ, and vertical velocity v_z at τ_500nm = 1. The time slice of mv07 shows the inward motion of PG 7b (left) and the outward motion of PG 7a (right). Contours correspond to I_out = 0.75 I_ph, and the horizontal dashed lines mark the time corresponding to frame 14 of mv07 displayed in Fig. 8. The intensity slice of mv08 shows the changing direction of PG 8. Contours correspond to I_out = 0.9 I_ph.