Extragalactic electromagnetic cascades and cascade gamma-ray emission in magnetic fields of various strength

We discuss the magnetic field influence on diffuse gamma-ray emission from extragalactic electromagnetic cascades initiated by ultra-high energy cosmic rays. Regions in space vary considerably in field strength: it is possibly of 10^(-12) G and lower in voids, of ~10^(-6) G inside galaxies, galactic clusters and groups, of ~10^(-7) G around them, and of ~ 10^(-8)-10^(-9) G in filaments. Structures having fields higher than in voids occupy comparatively small fraction of the Universe, so they affect weakly on cascade emission. Still knowledge of this influence may be relevant studying large-scale component of the extragalactic magnetic field and to the search for exotic particles, as in the latter case contribution of all components to extragalactic gamma-ray background should be known, one of which is cascade emission. To study magnetic field effect we simulate particle propagation in homogeneous magnetic field of ~10^(-6), 10^(-9), and 10^(-12) G and lower. It is found that in fields of ~10^(-9) G and lower the spectra of diffuse cascade gamma-rays at energies E<=10^17 eV coincide. Thus no specific models of EGMF are required to study contribution of cascade emission in the extragalactic gamma-ray background at E<=10^17 eV. In the case of uniform field of 10^(-6) G (which seems to be unrealistic), this inference is valid in the energy range of ~10^7-10^9 eV. Results obtained can be also used studying large-scale component of the extragalactic magnetic field.Comment: 13 pages, 3 figures, accepted in Advances in Space Research, avaliable online 26 Sept 202

Magnetic deflections and possible sources of the ultra-high-energy cosmic rays in the AGASA-HiRes-Yakutsk cluster

The cluster of ultra-high-energy cosmic rays observed by the AGASA, HiRes and Yakutsk experiments is studied with respect to possible deflections of particles in regular magnetic fields. Best-fit positions of a potential source of these clustered particles are found, with account of the errors in energy estimation, both in the frameworks of particular models of the Galactic magnetic field and treating the direction and the amount of deflection as free parameters. The study suggests that an unknown regular component of either Galactic or extragalactic magnetic field may dominate over modelled components in the direction of the cluster. Possible sources of the cosmic rays in that direction are considered.Comment: 18 pages, 3 eps figures, iopart.cl

Possible Origin of Clusters in Ultra-High-Energy Cosmic rays

We estimate the detection rate of ultrahigh-energy cosmic rays on ground based arrays by assuming that the cosmic ray sources are active galactic nuclei. We analyse the cases of detection of clusters, several particles that arrived, within the error limits, from the same area of the sky. The adopted model is shown to explain the detection rate of clusters on the AGASA array.Comment: 6 pages; to be published in Astronomy Letters, v.31, 200