We present the main characteristics of cosmic ray population in the atmosphere and its variability (11-and 22-year solar cycle variations, solar protons originating from powerful solar flares, energetic electron precipitation during geomagnetic disturbances and Forbush decreases of cosmic rays). The experimental data were obtained from the long-term cosmic ray monitoring in the atmosphere from ...

As ultra-high energy cosmic ray protons propagate through the universe, they undergo photo-meson interactions with the cosmic microwave background, generating the ‘cosmogenic’ neutrino flux. If a substantial fraction of the cosmic ray primaries are heavy nuclei rather than protons, however, they would preferentially lose energy through photo-disintegration, so the corresponding neutrino flux ma...

An interesting accident of nature is that the peak of the cosmic ray spectrum, for both protons and heavier nuclei, occurs near the pion production threshold. The Boltzmann transport equation contains a term which is the cosmic ray flux multiplied by the cross section. Therefore when considering pion and kaon production from proton-proton reactions, small cross sections at low energy can be as ...

We show that cosmic-ray observations set a model-independent upper bound of En Fn,2 310 GeV/cm s sr to the intensity of high-energy neutrinos produced by photo-meson ~or p-p! interactions in sources of size not much larger than the proton photo-meson ~or p-p! mean-free-path. This bound applies, in particular, to neutrino production by either AGN jets or GRBs. The upper limit is two orders of ma...

Cosmic Rays (CR) travel at speeds essentially indistinguishable from the speed of light. However whilst travelling through magnetic fields, both regular and turbulent, they are delayed behind the light since they are usually charged particles and their paths are not linear. Those delays can be so long that they are an impediment to correctly identifying sources which may be variable in time. Fu...

We present here a comparison of interaction models commonly used for simulating cosmic ray shower development in the atmosphere at energies greater than 1 TeV. The implementations of these models in CORSIKA and the FLUKA transport and interaction code are relevant for extensive air shower experiments, neutrino telescopes, and gamma-ray surfacebased detectors. We compare the pion, kaon, charmed ...