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

(abridged) The interpretation of Faraday rotation measure maps of AGNs withingalaxy clusters has revealed regions, $\sim 50-100$ kpc, that are populatedwith large, $\sim 30 \mu$ G magnetic fields. The magnetic energy of thesecoherent regions is $\sim 10^{59-60}$ ergs, and the total magnetic energy overthe whole cluster ($\sim 1$ Mpc across) is expected to be even larger. Asequence of physical processes that are responsible for the production,redistribution and dissipation of these magnetic fields is proposed. Thesefields are associated with single AGNs within the cluster and therefore withall galaxies during their AGN phase, simply because only the centralsupermassive black holes ($\sim 10^8 M_{\odot}$) have an accessible energy,$\sim 10^{61}$ ergs. We propose an $\alpha-\Omega$ dynamo process in anaccretion disk. The disk rotation naturally provides a large winding number,$\sim 10^{11}$ turns, sufficient to make both large gain and large flux. Thehelicity of the dynamo can be generated by the differential plume rotationderived from star-disk collisions. This helicity generation process has beendemonstrated in the laboratory and the dynamo gain was simulated numerically. Aliquid sodium analog of the dynamo is being built. Speculations are that theback reaction of the saturated dynamo will lead to the formation of aforce-free magnetic helix, which will carry the energy and flux of the dynamoaway from the accretion disk and redistribute the field within the clusters andgalaxy walls. The magnetic reconnection of a small fraction of this energylogically is the source of the AGN luminosity, and the remainder of the fieldenergy should then dominate the free energy of the present-day universe.Comment: invited review at the 2000 APS/DPP meeting, Quebec, 11 pages, 7 color figs (.jpg