Flare loop formation via slip-running reconnection. Top and side views show a set of field lines drawn at t = 20,20.3,20.7  t_A. The field lines are integrated at each time from the same set of footpoints (anchored at their respective coordinates F₋). The panels show different locations of the moving footpoints within the positive magnetic polarity. The gray-scale image and the cyan/pink contourplots represent J_z(z = 0) and B_z(z = 0) as in Fig. 3a.