Origin and Propagation of Ultrahigh Energy Cosmic Rays
Origin of cosmic rays with the highest detected energies up to more than 1020 eV is discussed. The acceleration of these particles is associated with the most energetic extragalactic objects in the Universe – active galactic nuclei, gamma-ray bursts, magnetars, cosmological shocks, etc. Interactions with the background radiation in the intergalactic space change the composition of ultrahigh energy cosmic rays and lead to the suppression of their flux above about 5 1019 eV (the Greizen-Zatsepin-Kuzmin effect). The spectrum of ultrahigh energy cosmic rays produced by jets of active galactic nuclei is calculated.