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P.P. Kronberg, S.A. Colgate, H. Li, Q.W. Dufton (LANL)
The enormous size scales, and energy content of giant radio galaxies (GRG's) make them important testbeds for understanding both the acceleration of CR particles and the growth of magnetic flux. They impose stringent limits on propagation, particle acceleration times, magnetic field structures, and thermal gas densities. The GRGs' synchrotron emitting radio lobes are the largest non-gravitationally bound associations of energetic particles and magnetic fields in our universe, and their energy content is only exceeded by that of large galaxy clusters. From a detailed characterization of the relativistic plasmas in GRG's, combined with recent advances in understanding magnetic flux generation mechanisms, and magnetic reconnection theory, we conclude that their relativistic particles are accelerated very efficiently, probably by magnetic reconnection. The likely importance of reconnection is suggested, among other reasons, by the striking absence of strong shocks in GRG lobes, and it is consistent with recent work at LANL proposing that the magnetic energy is initially stored in force-free fields. This conclusion has wide-ranging astrophysical consequences: It implies that space-distributed magnetic reconnection is a primary mechanism in all extended, AGN-fed non-thermal extragalactic radio sources, including those embedded in galaxy clusters. It has implications for discriminating mechanisms for energy transfer away from the supermassive black hole energy source, and for understanding the source of extraglactic cosmic rays.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.