Right panels: temporal evolution of Si iv line parameters averaged over the region where the line shows a satellite (black: intensity; red: velocity). Dotted and dashed vertical lines show the beginning and end of shock front passages, respectively. Positive velocities correspond to blueshifts. The times of zero velocity in the shock fronts are marked by green crosses. The main component’s peak intensity shows a minimum at these times. The lower right panel shows the temporal evolution of the satellite’s peak intensity. Left panels: temporal evolution of the average shock front of the nine shocks indicated by crosses in the upper right panel; time is given relative to the zero-crossing times of the main component’s Doppler shift. The intensities of the Si iv satellite and main component are anti-correlated.