Magnetic Fields in Young Galaxies
  We have studied the fate of initial magnetic fields in the hot halo gas out of which the visible parts of galaxies form, using three-dimensional numerical MHD-experiments. The halo gas undergoes compression by several orders of magnitude in the subsonic cooling flow that forms the cold disk. The magnetic field is carried along and is amplified considerably in the process, reaching muG levels for reasonable values of the initial ratio of magnetic to thermal energy density. 
A . Nordlund, O. E. Rognvaldsson