Magnetograms at −0.39 Å and B_∥ estimates on a large concentration for different Δt. The plus symbols (+) and crosses (×) mark the pixels shown in the two upper and lower rows of Fig. 11, respectively. The yellow rectangle delimits the region displayed on the right-hand side. Same layout as in Fig. 3. A movie showing the temporal evolution of the parameters displayed in this figure is available online.