Evolution of traced magnetic field lines. On the left, traced magnetic field lines are plotted over the vertical component of the photospheric magnetic field. In the middle, the position of the corresponding footpoints is marked over the sum of resistive and viscous heating terms integrated over the height range [0.6 − 3.8] Mm (second column) and [2.7 − 7] Mm (third column). On the right, we show the projection of the traced field lines to the z-axis. The background shows density along the horizontal cut at y = 28 Mm. The movie is available online.