Cosmic ray injection at SNR shocks: a laboratory for radio galaxy plasma physics?

The standard paradigm for extragalactic radio sources assumes that a description in terms of single-fluid MHD, adiabatic work, and radiation losses should provide an adequate model for the observed radiation and morphology. However this approach omits several physical elements that are now standard in other branches of laboratory, space, and astrophysical plasma physics, and we examine whether current observations of extragalactic radio sources motivate extensions to the standard paradigm. Supernova remnants are analogous to extragalactic radio sources in producing synchrotron radiation from radio to X-ray wavelengths, and electron energies as high as 10(14) eV axe required in some cases. Diffusive shock acceleration can generate these electrons from a mildly relativistic population, but the 'injection' problem of prior acceleration of background electrons to mildly relativistic energies has remained. Here we describe the 'bootstrap' solution of the electron injection problem, by which a shock-reflected proton population drives collective plasma instabilities, which in turn excite waves in the plasma which accelerate thermal electrons to mildly relativistic energies. The physical processes incorporated in this solution lie outside the standard paradigm for extragalactic radio sources, and we discuss their potential relevance