On the sources of cosmic ray electrons

Abstract

The spectrum of cosmic ray electrons is discussed in terms of the contributions from discrete sources distributed over the Galaxy. The analysis shows that one needs sources situated within a few hundred parsecs of the solar system, in order that the radiative losses of energy do not induce a premature cutoff in the energy spectrum. If the mean spatial density of the sources is roughly uniform over the galactic plane, then there should be at least 30,000 active sources accelerating cosmic rays in the Galaxy. Therefore it is very unlikely that supernovae are the only sources of cosmic ray electrons in the energy range 1-1000 GeV.