Cosmic ray (CR) acceleration at the shock created by the expanding cocoons around active galactic nuclei (AGNs) is studied. It is shown that above the energy $10^{ 18}$ eV the overall energy spectrum of CRs, produced during the AGN evolution and released in the intergalactic space, has the form $N\propto \epsilon^{ -\gamma}$, with $\gamma\approx 2.6$, which extends up to $\epsilon_{ max}\sim 10^{ 20}$ eV. It is concluded that cocoons shocks have to be considered as a main source of extragalactic CRs, which together with Galactic supernova remnants provide the observed CR spectrum.
Categories: astro-ph