Colour coded images of our model galaxies: from top to the bottom models 75, 76 and 77, from left to right: azimuthal component of magnetic field, azimuthal component of large-scale magnetic field and azimuthal component of small-scale magnetic field at approximate times 13.2 Gyr. The large-scale field is averaged over 1 kpc. The continuous contours delineate the regions (“arms”) where field is injected; these rotate rigidly, with pattern speed such that the corotation radius is at fractional radius r ≈ 0.7.