Gnatyk R. Sources, energy spectrum, and chemical composition of ultra-high energy cosmic rays

We investigate the energy spectrum, chemical composition of ultra-high energy cosmic rays (UHECR), and search for potential sources of extremely high energy cosmic rays (EHECR). We analyze the chemical composition of the UHECR on the base of developed cosmic ray spectrum models and calculated mean depths of shower maxima for different partial contribution of proton, Helium and Iron nuclei in total observed flux, taking into account a modification factor for the description of UHECR interaction with the cosmic microwave background. We propose a new interpretation of the KASCADE-Grande results about the presence of light component in the energy range 10^17-10^18 eV as signature of extragalactic proton component with energy spectrum additionally modified by the proton diffusion in the intergalactic magnetic field. Taking into account the deflections of UHECR trajectories in Galactic and extragalactic magnetic fields we search for potential Galactic and extragalactic sources for two events - the triplet of cosmic rays with E > 10^20 eV and the event with highest energy E = 3.2*10^20 eV (FE-event). We show that potential source of triplet is magnetar SGR 1900+14, while potential sources of FE-event are close (< 40 Mpc) ordinary galaxies UGC 03574 and UGC 03394. We use the existing analytical solutions of the transport equation with the explicit determination of the contributions from scattered and unscattered particles to explain clustered events from transient sources. As examples, we consider the cases of transient activity of the nearest active galactic nucleus, Centaurus A, and the acceleration of UHECRs by a young millisecond pulsar in our Galaxy.