Selected magnetic field lines (left panels) and current density iso-surfaces (j = 0.5) (right panels) during magnetic reconnection in the Model A (low-density case). Different colours are used for magnetic field lines to demonstrate the change of connectivity. Blue lines originate almost at the centre of the footpoint at y ≈ 6.4; red lines originate almost at the centre of the footpoint (y ≈  − 6.4); other lines belonging to the twisted fluxtube are shown in green. The corresponding times are shown at the lower left corners.