ON THE DIFFUSE GAMMA-RADIATION AT ULTRA-HIGH ENERGIES, E-GAMMA GREATER-THAN-OR-EQUAL-TO 1014 EV

We have calculated the diffuse fluxes of ultra-high-energy gamma radiation (Eγ ≳ 1014 eV). The following sources are considered: pp → π0 X scattering of Galactic cosmic rays in the interstellar gas, the interaction of metagalactic cosmic rays with the microwave background radiation (p + γb→p+tild;+e++e-) followed by Compton scattering of electrons on microwave photons (e+γb →e′+γ′), the p+γb→p+π0 interactions of metagalactic cosmic rays followed by π0→2γ decays, and point extragalactic sources. It is shown that the flux of diffuse gamma radiation from the Galactic center at energies greater than 1014 eV is 6.6 × 10-13 10-2 s-1 sr-1, and therefore it can be detected by the existing extensive air shower (EAS) arrays. A considerable flux of isotropic gamma radiation is produced as a result of the interactions of ultra-high-energy cosmic rays with the microwave background radiation (p+γb→p+e++e-, e+γb→e′+γ′) if cosmic rays observed at E > 1018 eV are metagalactic protons. This flux dominates in the direction perpendicular to the Galactic plane.