Related papers: The cosmic ray luminosity of the nearby active gal…
The bulk of observed ultrahigh energy cosmic rays could be light or heavier elements, and originate from an either steady or transient population of sources. This leaves us with four general categories of sources. Energetic requirements set…
The cosmic ray spectrum has been shown to extend well beyond 10^20 eV. With nearly 20 events observed in the last 40 years, it is now established that particles are accelerated or produced in the universe with energy near 10^21 eV. In all…
We derive observational consequences of the hypothesis that cosmic rays (CR's) of energy $>10^{19}eV$ originate in the same cosmological objects producing gamma-ray bursts (GRB's). Inter-galactic magnetic fields $\gtrsim 10^{-12} G$ are…
It is generally regarded that the bulk of cosmic rays originate in the Galaxy and that those below the 'knee' (the rapid steepening in the energy spectrum) at a few PeV come from Galactic supernovae, the particles being accelerated by the…
The mass composition of high energy cosmic rays depends on their production, acceleration, and propagation. The study of cosmic ray composition can therefore reveal hints of the origin of these particles. At the South Pole, the IceCube…
The latest results on the sky distribution of ultra-high energy cosmic ray sources have consequences for their nature and time structure. If the sources accelerate predominantly nuclei of atomic number A and charge Z and emit continuously,…
The Pierre Auger Collaboration discovered, in a solid angle of radius about 18\degree, a local group of cosmic rays having energies in the region E0 \geq 5.5\times1019 eV and coming from the region of the Gen A radio galaxy, whose galactic…
We present convenient formulae for the energy losses of energetic atomic nuclei over the entire energy range relevant to the physics of cosmic rays. Results are applied to a leaky-box equation with a complete loss term. Thereby we derive…
The propagation of cosmic iron nuclei with energies above 10^19 eV from their sources to the Galaxy is discussed by assuming that cosmic rays at ultra-high energies are of extragalactic origin. In extragalactic space, cosmic nuclei interact…
Cosmic rays (CRs) are protons and atomic nuclei that flow into our Solar system and reach the Earth with energies of up to ~10^21 eV. The sources of ultra-high energy cosmic rays (UHECRs) with E >~ 10^19 eV remain unknown, although there…
Physics beyond the standard model might imply the cosmological production of particles with grand unification scale energies. Nucleons and gamma-rays from such processes are candidates for the cosmic rays observed beyond 100 EeV [10**(20)…
A method is developed to search for air showers initiated by photons using data recorded by the surface detector of the Auger Observatory. The approach is based on observables sensitive to the longitudinal shower development, the signal…
The little we do know of the physical conditions in gamma-ray bursters makes them conducive to the acceleration of high-energy cosmic rays, especially if they are at cosmological distances. We find that, with the observed statistics and…
We present the results of an analysis of the large angular scale distribution of the arrival directions of cosmic rays with energy above 4 EeV detected at the Pierre Auger Observatory including for the first time events with zenith angle…
The detection of cosmic rays with energy around and in excess of $10^{20}$ eV raises many questions that future experiments will help answering to. I address here my view of some of these open issues, as they are now and as they might be…
Measurements of anisotropies in the arrival directions of ultra-high-energy cosmic rays are crucial to pinpoint their sources, which are yet to be discovered. A dipolar anisotropy in right ascension above 8~EeV has been detected by the…
We present spectra and mass composition of cosmic rays incoming to the Earth in the energy range (0.5-2)10^20 eV. As their sources we consider Seyfert galaxies located at distances < 40 Mpc, following an acceleration model for such…
Recent astronomical observations reveal that Active Galactic Nuclei (AGN) are sources of high-energy radiation. For example, the Fermi-LAT and Hess telescopes have detected gamma-ray emissions from the cores of several types of AGN's. Even…
The high energy spectrum of cosmic rays presents three distinct traits, the second knee, the ankle, and the GZK cutoff and as such, a thorough understanding of cosmic rays encompasses the study of these three features. It is in the second…
The present situation with regard to experimental data on ultra high-energy cosmic rays is briefly reviewed. Whilst detailed knowledge of the shape of the energy spectrum is still lacking, it is clear that events above 10^20 eV do exist.…