Estimate of the primordial magnetic field helicity

Electroweak baryogenesis proceeds via changes in the non-Abelian Chem-Simons number. It is argued that these changes generate a primordial magnetic field with left-handed helicity. The helicity density of the primordial magnetic field today is then estimated to be given by similar to 10(2)n(b), where n(b) similar to 10(-6) /cm(3) is the present cosmological baryon number density. With certain assumptions about the inverse cascade we find that the field strength at recombination is similar to 10(-13) G on a comoving coherence scale similar to0.1 pc.