Butterfly diagram at a cylindrical radius of 0.015 R_⊙. The left two panels of the plot show the equal-mass merger, the right two panels the unequal-mass merger. The panels show the time evolution of the mean azimuthal (first and third panel) and radial (second and fourth panel) magnetic field versus height. The radial magnetic field shows the outward moving patterns that are characteristic for the MRI. The azimuthal field becomes a large-scale ordered, anti-aligned field.