Horizontal motion of small loop-like features. The trajectories A to D show the centre of the respective features identified in Fig. 3 as a function of time (colour-coded) over 140 s (after 18:54:11 UT). The error estimate for the position from the ellipse fitting procedure is approximately 0.5 pixels or 0.05′′ (half a tick mark). For comparison, the trajectory labelled “cent.” shows the mean position of the four loop-like features A to D. See Sect. 3.1.