Both the primodial field concept and the galactic dynamo theory require some magnetic field to start with. The dynamo has the advantage that it can amplify the seed magnetic field by a factor of 103 or more. In the non-linear dynamo the amplification factor could be even greater. With the accepted values of intergalactic magnetic field of ~ 10-10 Gauss (Ruzmaikin and Sokoloff, 1977) we may have to look for other sources of seed fields for amplification by a dynamo process.
One of the most important processes for the creation of a minute magnetic field is the 'Biermann battery' (Biermann, 1950). When applied to a galaxy the concept requires small turbulent cells which through charge separation would give small currents and hence magnetic fields. The concept of transferring this scenario to galactic scales failed (e.g. Hoyle, 1958) since enormous electromotive force would be required. One way out, which was studied by Hoyle and Ireland (1961), was to postulate helical magnetic fields.
A recent development in this area comes from the observations of CO rings and of poloidal magnetic fields in many mildly active galaxies. CO rings have been seen in the inner parts of M82 (Lo et al., 1987; Nakai et al., 1987; Loiseau et al., 1990), NGC1097 (Gerin et al., 1988), NGC4945, NGC1808, NGC 1068, etc. Also in these galaxies strong evidence for poloidal magnetic fields (Z-fields) was found either by optical studies or in radio polarization. This scenario was studied by Lesch et al. (1989). By applying the battery effect to give charge separation in the inner CO ring a small seed field can be created. This in turn can be amplified by compression and turbulent stretching. Possibly the poloidal field in the nucleus of a galaxy can in turn be amplified to give the observed azimuthal fields in the spiral arms.