Column density contours for the pure hydrodynamic run hyd (top) and the two MHD runs, mhd1r (middle) and mhd1t (bottom). In runs mhd1r and mhd1t the collision occurs along the z-axis. The initial magnetic field of run mhd1r is also along the z-axis, while that of mhd1t is along the y-axis. Time increases from left to right, as indicated in the plot labels. The mass-weighted projected magnetic field is shown with arrows, color coded according to its magnitude in μG.