Related papers: Cosmic Ray Models
A substantial increase of the mean logarithmic mass $<\ln A>$ of galactic cosmic rays {\em vs} energy has been observed . We study three effects that could explain this trend i) different source spectra for protons and heavy nuclei ii) a…
The highest energy cosmic rays observed possess macroscopic energies and their origin is likely to be associated with the most energetic processes in the Universe. Their existence triggered a flurry of theoretical explanations ranging from…
We discuss possible implications of a large interaction cross section between cosmic rays and dark matter particles due to new physics at the TeV scale. In particular, in models with extra dimensions and a low fundamental scale of gravity…
I give a concise introduction into high energy cosmic ray physics, including also few related aspects of high energy gamma-ray and neutrino astrophysics. The main emphasis is placed on astrophysical questions, and the level of the…
The propagation of ultra high energy cosmic rays in Galactic and extragalactic magnetic fields is investigated in the present paper. The motion of charged particles of different energies and chemical composition is simulated using different…
The Galactic cosmic ray spectrum is a remarkably straight power law. Our current understanding is that the dominant sources that accelerate cosmic rays up to the knee ($3 \times 10^{15}$ eV) or perhaps even the ankle ($3 \times 10^{18}$…
We discuss theoretical issues and experimental data that brought the ultra high energy cosmic rays in the list of Nature's greatest puzzles. After many years of research we still do not know how astrophysical acceleration processes can…
The cosmological gamma-ray burst (GRB) model for the production of ultra- high energy cosmic rays is described, and the current observational evidence which support it discussed. Several predictions of the model are presented, which would…
Our knowledge of the high-energy universe is undergoing a period of rapid change as new astronomical detectors of high-energy radiation start to operate at their design sensitivities. Now is a boomtime for high-energy astrophysics, with new…
The origin of cosmic rays remains an unresolved fundamental problem in astrophysics. The synergy of multiple observational probes, including the energy spectra, the mass composition, and anisotropy is a viable way to jointly uncover this…
Diffusive shock acceleration operating at expanding supernova remnant shells is by far the most popular model for the origin of galactic cosmic rays. Despite the general consensus received by this model, an unambiguous and conclusive proof…
We give a summary of the theoretical attempts to make sense of the observational data concerning the highest energy cosmic rays, (E > 3x10^{19} eV).
We propose that the knee in the cosmic ray spectrum at energies E ~ 10^{15.5} eV is due to "new physics", namely to a channel in the high energy (~ TeV in the CM) proton interactions hitherto unaccounted for in estimating the energies of…
The ARGO--YBJ experiment has been in stable data taking for more than five years at the Yangbajing cosmic ray observatory (Tibet, P.R. China, 4300 m a.s.l.). The detector collected about $5\times10^{11}$ events in a wide energy range from…
Recent balloon-borne and satellite experiments have established new features in the behavior of the spectra of cosmic rays. An analysis of all the data showed that hardening of most abundant primary cosmic ray nuclei spectra with increasing…
We present the results of a study that simulates trajectories of ultra-high energy cosmic rays from Centaurus A to Earth, for particle rigidities from $E/Z = 2$ EV to 100 EV, i.e., covering the possibility of primary particles as heavy as…
Combined data from gamma-ray telescopes and cosmic-ray detectors have produced some new surprising insights regarding intergalactic and galactic magnetic fields, as well as extragalactic background light. We review some recent advances,…
The physics results of high energy gamma-ray astronomy are reported, emphasizing recent achievements with ground-based detectors. This includes some of the instrumental developments and latest projects. The fundamental contribution of the…
Gamma-ray Astronomy studies cosmic accelerators through their electromagnetic radiation in the energy range between ~100 MeV and ~100 TeV. The present most sensitive observations in this energy band are performed, from space, by the Large…
This is a written version of a series of lectures aimed at graduate students in astrophysics/particle theory/particle experiment. In the first part, we explain the important progress made in recent years towards understanding the…