Cartoon of the interaction between the shock front and the HT. Before the interaction (left) the surface brightness of the HT progressively declines from the head to the tail. The right panel represents the current situation: the shock has passed through the last part of the tail that appears brighter because of the re-energisation undergone by the electrons. The bright spot is where the tail is currently shocked. The shock passage also caused the bending of the tail in the direction parallel to the shock itself.