The notion that collisionless plasma shocks can accelerate charged particles into high energies resulting into the observed Cosmic Ray Spectrum, has been around for many years and by now it is widely accepted that this process can account for the majority of the energetic, non-thermal particle distributions that we infer in various astrophysical environments. The work of the late 70s by a number of authors (e.g. Krymsky (1977}, Bell (1978a,1978b), etc) established in principle the basic mechanism of particle (Fermi) diffusive acceleration, in non-relativistic shocks. Since then, considerable work has been done analytically and numerically on the subject, however questions still need to be answered on this acceleration mechanism especially at relativistic shock speeds. Here, the role of the particle acceleration in astrophysical shocks is reviewed and we discuss their potential energy contribution to the observed Cosmic Ray Spectrum.
to appear in proccedings of the Carpathian Summer School of Physics Sinaia Romania 2007
- Pub Date:
- cosmic ray spectrum;
- particle acceleration