Other
Scientific paper
Nov 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002aps..dppri2004k&link_type=abstract
American Physical Society, 44th Annual Meeting of the Division of Plasma , abstract #RI2.004
Other
Scientific paper
It is now widely accepted that the only plausible energy source for intergalactic magnetic fields is gravitational, e.g. as opposed to the aggregate thermonuclear energy from stars. There are two sufficiently large gravitational energy reservoirs: (1) the large scale kinetic energy from intergalactic matter flows, and (2) the gravitational infall energy of supermassive black holes (BH) that have been found to be nearly ubiquitous in the centers of medium to large galaxies. The gravitational infall energy of the galaxies themselves, and their aggregate stellar thermonuclear energy are both inadequate. I will focus on (2), beginning with an analysis of the very largest megaparsec-scale (Mpc) radio galaxies. I will discuss why those Mpc-scale, ``giant'' radio galaxies are the best independent calibrators, and calorimeters of BH energy release into intergalactic (i.g.) space from individual galaxy systems. Furthermore radio galaxies and quasars are the most likely primary source of the magnetic energy in intergalactic space, even though there are other plausible sources of seed fields. Extraction of the BH energy by a coherent electrodynamic generator is an attractive mechanism, and again the giant radio sources provide an interesting test for this class of model. Their total energy, large scale field ordering, cosmic ray (CR) electron loss timescales and morphology all appear consistent with a coherent flux generator that extracts magnetic energy from an accretion disk around the central ˜ 10^8 M_sun galactic black hole. Contrary to what has been widely believed, the physical properties of the giants argue against shocks as the primary mechanism for creating magnetic flux and accelerating CR particles in the extended radio sources. This leaves magnetic reconnection as the most likely primary CR acceleration mechanism in radio sources and by implication for intergalactic cosmic rays, whose plasma β may be of order unity. If so, then shock acceleration in intergalactic magneto-plasmas is a secondary mechanism, which serves to re-energize CR's that were originally accelerated, probably by magnetic reconnection, in radio galaxies and quasars. Given the existence of galactic supermassive BH's, the first stages of this process appears explained by the ``Los Alamos'' models of Li et al. and Colgate et al.. These describe how the accretion disk (infall) energy can converted into force-free, collimated magnetic fields that efficiently carry away the gravitational energy in Poynting flux flows. The subsequent conversion of the electromagnetic energy into cosmic rays up to Mpc scales has yet to be completely understood.
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