3D visualization of the location of the bright loop at time t = 14 min. The green lines show the fieldlines roughly outlining the volume of the first bright loop appearing in the simulation. The bottom plane shows the vertical component of the photospheric magnetic field. A density cut in the vertical plane halfway between the footpoints of the loops perpendicular to the loop is indicated by the large green square. On this cut red indicates chromospheric densities, and blue enhanced coronal densities of about 10⁹ cm^-3. Lower densities in the corona are transparent. The black square in dashed line on the midplane indicates the field of view in Fig. 8. See Sect. 5.