Left column: temperature maps at 0 km height of the simulation box showing the development of the dark core within the exploding granule shown in Fig. 8 for different times. The same time t = 0 is chosen for both plots. Right column: cut through the x − z − plane of the atmosphere along the red line in the images on the left. Coloured background shows the v_z velocity, and the black arrows represent the projection of the velocity vector onto the x − z − plane. Additional contours show the magnetic field strength at levels of 10 G (pink), 20 G (blue), 30 G (yellow), and 40 G (green).