Explanations of the spectral shape in the energy range 10 14 -10 20 eV

Abstract

There is evidence suggesting an increase in slope of the energy spectrum of primary cosmic-ray nuclei at about 3 x 1015 eV. Alternative explanations are advanced for this change, related to diffusion of particles of galactic origin or black body cut-off effects for particles of extra-galactic origin. At higher energies there appear to be particles of energy up to 1020 eV. The evidence will be examined critically and alternative explanations put forward for the spectral shape in this region.