Supernovae and the origin of cosmic rays

Abstract

This thesis contains a review of our present knowledge about the cosmic ray flux and about supernovae and their-remnants. It contains an attempt to examine the widely- held belief" that cosmic rays are produced principally in supernova remnants by work on essentially four topics' connected with the production of cosmic rays in supernova- remnants;-a) The likely surface density of supernova remnants in the Galaxy as a function of distance from the Galactic centre. It is shown that the general shape of the surface density curve consists of a large peak near the Galactic centre followed by a fairly, rapid fall to a low value at the edge of the Galaxy. The actual values of surface density are very dependent on the distances of the observed supernova remnants, which in turn depend on the adopted surface brightness - diameter relationship, b) The predicted slope of the electron spectrum between energies of 4x10(^8) and 10(^10) eV, assuming it results from the addition of the energy spectra of all the supernova remnants in the Galaxy. The observed electron energy spectrum in this range is at present too uncertain to be able to say whether or not it disagrees with that predicted. c) The time of production of cosmic rays in supernova remnants, if they are to traverse no more matter than that which is inferred from the ratio of abundances of the L to M groups in the cosmic rays. It is found that if the cosmic rays are produced inside the expanding remnant, then the matter traversal constraint means that they must be produced 2 years or so after the explosion. d) The expected distribution of gamma rays in the Galaxy from supernova remnants of diameters less than 50 parsecs. It is shown that in all probability the gamma ray results give direct evidence of the presence of cosmic rays in supernova remnants but that supernova remnants alone cannot be responsible for the whole of the gamma ray flux, at least on present gamma ray production models.