We perform Monte Carlo simulations of cosmic-ray induced hard X-ray emission in the Earth’s atmosphere. We find that the shape of the spectrum emergent from the atmosphere in the energy range ∼25–300 keV is determined by Compton scattering and photoabsorption and is virtually independent of the incident cosmic ray spectrum. We provide a fitting formula for the spectral intensity as a function o...

Aims. We use 5 years of Fermi-LAT data towards the Galactic-centre giant molecular cloud complex, Sagittarius B, to test questions of how well-mixed the Galactic component of cosmic rays are and what the level of the cosmic-ray sea in different parts of the Galaxy is. Methods. We use dust-opacity maps from the Planck satellite to obtain independent methods for background subtraction and an esti...

Cosmic rays produced in cluster accretion and merger shocks provide pressure to the intracluster medium (ICM) and affect the mass estimates of galaxy clusters. Although direct evidence for cosmic-ray ions in the ICM is still lacking, they produce γ-ray emission through the decay of neutral pions produced in their collisions with ICM nucleons. We investigate the capability of the Gamma-ray Large...

We review the current state and future prospect of ultra high energy cosmic ray physics and the relationship between cosmic rays and gamma-ray astrophysics.