On the Biermann 'battery' process in uniformly rotating, chemically inhomogeneous stars

A previous author has pointed out that if the mean molecular weight μ in a stellar radiative zone has a non-spherical distribution, then the partial pressure gradient per electron will in general have a curl and so will act as a Biermann 'battery'. Examples of battery-maintained toroidal magnetic fields are constructed, but with the associated currents constrained to flow along the lines of a primeval poloidal field of quadrupole or displaced dipole structure. Attention is focused on the self-consistent cases, in which the star rotates uniformly and the μ-distribution is fixed by the mutual cancellation of the Eddington-Sweet 'Ω-currents' and the 'μ-currents'. The fields are weaker than those found by Biermann in his original study of non-uniformly rotating but chemically homogeneous stars, but in rapid rotators are comparable in strength with the estimated internal poloidal field in an Ap star. (author)