This work presents preliminary results for the time-dependent cosmic-ray propagation in the Galaxy by a fully 3-dimensional Monte Carlo simulation. The distribution of cosmic-rays (both protons and helium nuclei) in the Galaxy is studied on various spatial scales for both constant and variable cosmicray sources. The continuous diffuse gamma-ray emission produced by cosmic-rays during the propag...

We describe the results of a hybrid matrix{Monte Carlo calculation of cascading of UHE cosmic rays through the cosmic background radiation elds over cosmological distances. We calculate the-ray and neutrino emission that results from the cascade, as well as the eeect of cascading on the primary spectrum. We discuss the results for various cosmic ray injection spectra.

In the atmosphere cosmic rays produce Be-10, C-14 and other radionuclides. It is commonly supposed that the concentrations of these radionuclides (Be-10 in polar ice and C-14 in tree rings) are good proxies of cosmic ray fluxes impinging on the top of the atmosphere. But before the precipitation on the Earth’s surface these elements spend several years in the atmosphere. The stirring of their c...

[1] We present a quasi-steady two-dimensional (axisymmetric) model of the heliospheric transport of galactic cosmic rays. The model is based on stochastic simulation techniques and includes all the modulation mechanisms that cosmic rays experience in the heliosphere: convection, adiabatic cooling, diffusion, and drifts. A special emphasis is given to the cosmic ray transport in the vicinity of ...

Clusters of galaxies have not yet been detected at gamma-ray frequencies; however, the recently launched Fermi Gamma-ray Space Telescope, formerly known as GLAST, could provide the first detections in the near future. Clusters are expected to emit gamma rays as a result of (1) a population of high-energy primary and re-accelerated secondary cosmic rays fueled by structure formation and merger s...

Molecular clouds are expected to emit non-thermal radiation due to cosmic ray interactions in the dense magnetized gas. Such emission is amplified if a cloud is located close to an accelerator of cosmic rays and if cosmic rays can leave the accelerator and diffusively reach the cloud. We consider the situation in which a molecular cloud is located in the proximity of a supernova remnant which i...

Centaurus A, the cosmic ray accelerator a few Mpc away from us is one of the nearest sources of extremely high energy cosmic rays. It would be interesting to see whether the gamma ray data currently available from Centaurus A in the GeV-TeV energy band can be explained with only proton proton interactions. We show that to be consistent with the gamma ray luminosity observed in the GeV-TeV energ...

We suggest that the luminous extreme ultraviolet (EUV) emission which has been detected recently from clusters of galaxies is Inverse Compton (IC) scattering of Cosmic Microwave Background (CMB) radiation by low energy cosmic ray electrons in the intracluster medium. The cosmic ray electrons would have Lorentz factors of γ ∼ 300, and would lose energy primarily by emitting EUV radiation. These ...

Using a linear stability analysis and two and three-dimensional nonlinear simulations, we study the physics of buoyancy instabilities in a combined thermal and relativistic (cosmic ray) plasma, motivated by the application to clusters of galaxies. We argue that cosmic ray diffusion is likely to be slow compared to the buoyancy time on large length scales, so that cosmic rays are effectively adi...