Column density of runs R3 (left) and R5 (right), i.e. weakly magnetised runs, for two snapshots. For run R3 even though the magnetic intensity is 3 times weaker than for run R2, the disc is only marginally larger. Two noticeable differences however are that the disc presents strong and persistent spiral arms and that there remains large-scale spiral arms outside the disc. As can be seen, run R5 (which has a magnetic intensity about 4 times lower than run R2) fragments in 2 objects.