Primordial magnetic fields, right electrons, and the Abelian anomaly

In the standard model there are charges with Abelian anomaly only (e.g., right-handed electron number) which are effectively conserved in the early Universe until some time shortly before the electroweak scale. A state at finite chemical potential of such a charge, possibly arising due to asymmetries produced at the grand unified theory scale, is unstable to the generation of hypercharge magnetic field. Quite large magnetic fields (similar to 10(22) G at T similar to 100 GeV with typical inhomogeneity scale similar to 10(6)/T) can be generated. These fields may be of cosmological interest, potentially acting as seeds for amplification to larger scale magnetic fields through nonlinear mechanisms. Previously derived bounds on exotic B - L violating operators may also be evaded.