The Magnetic Fields of the Universe and Their Origin

Abstract

Recent rotation measure observations of a dozen or so galaxy clusters have revealed a surprisingly large amount of magnetic fields, whose estimated energy and flux are, on average, $\sim 10^{58}$ ergs and $\sim 10^{41}$ G cm$^2$, respectively. These quantities are so much larger than any coherent sums of individual galaxies within the cluster that an efficient galactic dynamo is required. We associate these fields with single AGNs within the cluster and therefore with all galaxies during their AGN phase. Only the central, massive black hole (BH) has the necessary binding energy, $\sim 10^{61}$ ergs. Only the accretion disk during the BH formation has the winding number, $\sim 10^{11}$ turns, necessary to make the gain and magnetic flux. We present a model of the BH accretion disk dynamo that might create these magnetic fields, where the helicity of the $α- Ω$ dynamo is driven by star-disk collisions. The back reaction of the saturated dynamo forms a force-free field helix that carries the energy and flux of the dynamo and redistributes them within the clusters.