Abstract
The cosmic-ray spectrum at 1019-1020 eV, reported by the Fly's Eye and the AGASA experiments, is shown to be consistent with a cosmological distribution of sources of protons, with a power-law generation spectrum d ln N/d ln E = -2.3 ± 0.5 and energy production rate of 4.5 ± 1.5 × 1044 ergs Mpc-3 yr-1. The two events measured above 1020 eV are not inconsistent with this model. Verifying the existence of a "blackbody cutoff," currently observed with low significance, would require ~30 observation years with existing experiments, but only ~1 year with the proposed ~5000 km2 detectors. For a cosmological source distribution, no anisotropy is expected in the angular distribution of events with energies up to ~5 × 1019 eV.
Export citation and abstract BibTeX RIS