GENERATION OF LARGE-SCALE MAGNETIC FIELDS FROM PRIMORDIAL DENSITY FLUCTUATIONS

Abstract

We investigate a generation of magnetic fields from cosmological density perturbations. In the primordial plasma before cosmological recombination, all of the materials except dark matter in the universe exist in the form of photons, electrons, and protons (and a small number of light elements). Due to the different scattering nature of photons off electrons and protons, electric currents and electric fields are inevitably induced, and thus magnetic fields are generated. We numerically obtain the power spectrum of magnetic fields over a wide range of scales, from k ~ 10−5 Mpc −1 to k ~ 109 Mpc −1. Implications of these cosmologically generated magnetic fields are discussed.