The origin of the magnetic fields of the universe: The plasma astrophysics of the free energy of the universe

Abstract

The interpretation of Faraday rotation measure maps of active galactic nuclei (AGNs) within galaxy clusters has revealed ordered or coherent regions, Lmag∼50−100 kpc (∼3×1023 cm), that are populated with large, ∼30 μG magnetic fields. The magnetic energy of these coherent regions is Lmag3(B2/8π)∼1059−60 ergs, and the total magnetic energy over the whole cluster (∼1 Mpc across) is expected to be even larger. Understanding the origin and role of these magnetic fields is a major challenge to plasma astrophysics. A sequence of physical processes that are responsible for the production, redistribution, and dissipation of these magnetic fields is proposed. These fields are associated with single AGNs within the cluster and therefore with all galaxies during their AGN (active galactic nucleus or quasar) phase, simply because only the central supermassive black holes (∼108M⊙) formed during the AGN phase have an accessible energy of formation, ∼1061 ergs, that can account for the magnetic field energy budget. An α–Ω dynamo process has been proposed that operates in an accretion disk around a black hole. The disk rotation naturally provides a large winding number, ∼1011 turns, sufficient to make both large gain and large flux. The helicity of the dynamo can be generated by the differential plume rotation derived from star-disk collisions. This helicity generation process has been demonstrated in the laboratory and the dynamo gain was simulated numerically. A liquid sodium analog of the dynamo is being built. Speculations are that the back reaction of the saturated dynamo will lead to the formation of a force-free magnetic helix, which will carry the energy and flux of the dynamo away from the accretion disk and redistribute the field within the clusters and galaxy walls. The magnetic reconnection of a small fraction of this energy logically is the source of the AGN (active galactic nucleus or quasar) luminosity, and the remainder of the field energy should then dominate the free energy of the present-day universe. The reconnection of this intergalactic field during a Hubble time is the only sufficient source of energy necessary to produce an extragalactic cosmic ray energy spectrum as observed in this galaxy, and at the same time allow this spectrum to escape to the galaxy voids faster than the GZK (blackbody radiation) loss.