The origin of galactic magnetic fields is a long-standing puzzle. The fields are very weak - on the order of a microtesla - and could have been generated from much weaker "seed" fields, although there have been few viable candidates. Now Kiyotomo Ichiki and colleagues at the National Astronomical Observatory of Japan have demonstrated that these weak fields could be a signature of the early history of the universe before protons and electrons combined to form atoms.
The idea is that density fluctuations in plasma could produce "winds" of photons from high-density regions to low-density ones. This wind would push electrons more than the heavier protons, and give rise to charge separations and rotating electric currents that could have seeded the magnetic fields we see today. The theory is even testable, as it would lead to magnetic fields in regions of space that are very empty of matter (free of stars and galaxies) - something that experiments could conceivably try to detect.
Further reading
Kiyotomo Ichiki et al Science DOI:10.1126/science.1120690, to appear in Science; online at Science Express: www.sciencemag.org/cgi/content/abstract/1120690.