A new interpretation of the alpha effect

Abstract

In a magnetized plasma the alpha effect represents a turbulently generated emf directed along the mean magnetic field. This emf is central to the understanding of turbulent generation of large-scale magnetic fields. The alpha effect is reevaluated in terms of ensemble-averaged properties of the magnetic fluctuation spectrum. The results indicate that it is current helicity as opposed to kinetic helicity that is required to produce an alpha effect.