A possible mechanism for generating galactic magnetic fields

We demonstrate that the Biermann battery mechanism for the creation of larg e-scale magnetic fields can arise in a simple model protogalaxy. Analytic c alculations and numerical simulations follow explicitly the generation of v orticity (and hence magnetic held) at the outward-moving shock that develop s as the protogalactic perturbation collapses. Shear angular momentum then distorts this field into a dipolelike configuration. The magnitude of the f ield created in the fully formed disk galaxy is estimated to be 10(-17) G, approximately what is needed as a seed for the galactic dynamo.