We perform Monte Carlo simulations of transrelativistic shear acceleration dedicated to a jet-cocoon system of active galactic nuclei. A certain fraction of galactic cosmic rays in a halo is entrained, and sufficiently high-energy particles can be injected to the reacceleration process and further accelerated up to 100 EeV. We show that the shear reacceleration mechanism leads to a hard spectrum of escaping cosmic rays, dLE/dE ∝ E −1 − E 0 , distinct from a conventional E −2 spectrum. The supersolar abundance of ultrahigh-energy nuclei is achieved due to injections at TeV-PeV energies. As a result, we find that the highest-energy spectrum and mass composition can be reasonably explained by our model without contradictions with the anisotropy data.
Abstract. We computed the energy spectra of the incident (on an air shower array) ultrahighenergy (E > 4⋅10 19 eV) cosmic rays (CRs) that were accelerated in nearby Seyfert nuclei at redshifts z≤ 0.0092 and in BL Lac objects. These were identified as possible CR sources in our previous works. For our calculations, we took the distribution of these sources over the sky from catalogs of active galactic nuclei. In accordance with the possible particle acceleration mechanisms, the initial CR spectrum was assumed to be monoenergetic for BL Lac objects and a power law for Seyfert nuclei. The CR energy losses in intergalactic space were computed by the Monte Carlo method. We considered the losses through photopion reactions with background radiation and the adiabatic losses. The artificial proton statistic was 10 5 for each case considered.The maximum energy of the CRs incident on an external air shower (EAS) array was found to be 10 21 eV, irrespective of where they were accelerated. The computed spectra of the particles incident on an EAS array agree with the measurements, which indirectly confirms the adopted acceleration models. At energies E≥10 20 eV, the spectrum of the protons from nearby Seyfert nuclei that reached an EAS array closely matches the spectrum of the particles from BL Lac objects. BL Lac objects are, on average, several hundred Mpc away. Therefore, it is hard to tell whether a blackbody cutoff exists or not by analyzing the shape of the measured spectrum at E≥ 5⋅10 19 eV.
The development of nuclear-electromagnetic cascade models in air in the late forties have shown informational content of the study of cores of extensive air showers (EAS). These investigations were the main goal in different experiments which were carried out over many years by a variety of methods. Outcomes of such investigations obtained in the HADRON experiment using an X-ray emulsion chamber (XREC) as a core detector are considered. The N e spectrum of EAS associated with γ-ray families, spectra of γ-rays (hadrons) in EAS cores and the N e dependence of the muon number, N µ , in EAS with γ-ray families are obtained for the first time at energies of 10 15-10 17 eV with this method. A number of new effects were observed, namely, an abnormal scaling violation in hadron spectra which are fundamentally different from model predictions, an excess of muon number in EAS associated with γ-ray families, and the penetrating component in EAS cores. It is supposed that the abnormal behavior of γ-ray spectra and N e dependence of the muon number are explained by the emergence of a penetrating component in the 1st PCR spectrum 'knee' range. Nuclear and astrophysical explanations of the origin of the penetrating component are discussed. The necessity of considering the contribution of a single close cosmic-ray source to explain the PCR spectrum in the knee range is noted.
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