Propagation of cosmic rays in extragalactic radio sources

The transport of charged particles which are scattered by random magnetic fields while they propagate along the diverging lines of force of a spatially inhomogeneous guiding field is described by the Boltzmann equation. Nearly rigorous solutions, based upon a matrix formulation of this problem, lead to a new interpretation of radio galaxies. A radio source is formed when electrons from a galactic explosion move coherently outward along the strongly diverging lines of a large scale guiding field centered on the galaxy. Far from the center, where the divergence becomes weak, the electrons are scattered into two slowly evolving, nearly isotropic, clouds which constitute the twin lobes of a typical source. In the early coherent phase, electrons are transported without adiabatic energy losses in static magnetic fields and without serious Compton/synchrotron energy losses in the relatively short time they take to reach the lobes. In the diffusive phase, the radio polarization is perpendicular to the source axis and the structures nearest the center, which are old ones that have drifted inward, have a steeper spectrum than those further out. In radio trail galaxies, where the velocity of the galaxy through an ambient medium exceeds the drift velocity of the diffusive clouds, this spatial variation of the spectral steepness is reversed. Thus, several basic observational features of extragalactic radio sources are explained in terms of fundamental transport theory. (author) rd;xin.new.tomi