Whether the first fields were self-generated in the first stellar systems, or were really primordial, it seems likely that the magnetic forces competed and interacted with gas dynamical and purely gravitational erects during the early collapse phase of galaxies. This eventuality presents a major challenge to theory, in that virtually all theoretical models of galaxy formation up to now invoke gravity and thermodynamics, and ignore the complicating effects of magnetic fields of comparable energy densities in the environment of collapsing and/or merging protogalaxies. Because magneto-plasmas are highly non-linear systems, there is an additional challenge purely from the computational standpoint to construct detailed galaxy evolution and large scale structure evolution models which incorporate magnetic fields. This is true whether such fields existed ab initio, or were generated and/or amplified concurrently with the formation of the first galaxies.
Although the standard - dynamo theory gives first order agreement with the observations, the scenario of a slow galactic field build-up over several billion years from a very weak seed field in the early universe seems unlikely to the main cause of current µG fields in galaxies. The general trend of much of the observational evidence and theory suggests that (i) magnetic fields were built up over times much shorter than a galaxy lifetime, and that (ii) spiral and starburst galaxies, as well as radio jet/lobe systems and starburst galaxies are able to regenerate, and perhaps even create fields to near-microgauss levels in timescales << 108 yr.
This implies that, even if pre-galactic seed fields existed before a `volcanic' epoch of widespread starburst-like activity in the compact, early universe, the first starbursters might have been capable of overwhelming this field with their own, stronger, ejected fields, along with metal-enriched gas, in powerful galactic winds over a short period of cosmic time. This proposed type of activity is the analogue of what we observe in starburst galaxies. Less certain, but also potentially effective IGM magnetizers are radio jet sources from before and during the quasar epoch, if they existed then. They have been demonstrated to effectively magnetize substantial volumes of the IGM with their own, self-amplified magnetic fields.
If the first stars and protogalaxies provided the seed fields which were quickly amplified to energy equilibrium with the protogalactic IGM, then we may have to consider a two-stage early galaxy formation scenario: the first stage of collapse occurred with very small, or no fields. Succeeding generations of galaxies then perhaps formed in microgauss-level fields which, within a few times 108 yr were produced, amplified and expelled by the first generation of stars and galaxies. The observations we have reviewed do not appear to rule out a scenario of this sort.
For illuminating discussions and/or the provision of new results prior to publication 1 am grateful to Rainer Beck, Peter Biermann, Alan Bridle, David Clarke, Rod Davies, Götz Golla, Fritz Krause, Russell Kulsrud, Harald Lesch, Richard Lovelace, Gene Parker, Rick Perley, Judith Perry, Bob Rosner, Vera Rubin, Marcin Sawicki, Michael Scarrott, Anwar Shukurov, Dmitry Sokoloff, Chris Thompson, Gerrit Verschuur and Richard Wielebinski. I also thank Tal Kenet for her comments, and assistance in the preparation of the manuscript.