Supernova envelope shock origin of cosmic rays - a review

The hydrodynamic shock origin of cosmic rays in the envelope of a Type I presupernova star is reviewed. The spectrum produced by the relativistic hydrodynamic shock is one power of E steeper than observed and so is unlikely to be the primary source of cosmic rays. On the other hand the possibility of accelerating ultrahigh energy particles to ≥ 1018 eV is unique to the shock mechanism and currently no other suggested galactic or extragalactic site is likely. The heavy nuclei are partially spalled in the shock transition and partially resynthesized in the postshock expansion for E ≤ 1015 eV dependent upon the large number of pairs in the post-shock fluid. Above this energy the shock progresses in the magnetized photosphere. The high energy limit is similarly ordered 1021 eV due to the coronal density of the presupernova star. The objection to SN shock accelerated cosmic rays by adiabatic deceleration is questioned on the basis of the Alfven wave scattering conditions. Ultrahigh energy particles escape because the wave excitation energy density is too low in the dimension of many Larmor radii necessary for scattering back to the SN remnant. Others escape if the energy density is too high. For all others between these two limits the immediately following matter of lower velocity and greater mass compresses and energizes previously trapped higher energy particles, allowing them to escape at energies still higher than originally shock ejected from the supernova