On galaxies as accelerators of cosmic rays

In the frame of large-scale structure of the Universe, cosmic rays (CRs) can be considered as a component of the intergalactic medium, which originate and accelerate inside galaxies, leave them, fill the intergalctic space and have possibility to enter other galaxies and continue acceleration.Multiple repeating, this process may, in principle, produce CRs with ultra-high energy.To estimate characteristics of this process, we consider a simple version, when a charged particle falls on a plane layer of ISM and is reflected from it.As is known, the diffusion approximation fails to get the time and path distributions, so we apply more proper tools for calculations.The time distribution is obtained via the analytical solution of the linearized Boltzmann equation, and the acceleration process is calculated by solving the integral reacceleration equation.In addition, our analysis takes a fractal (turbulent) properties of ISM into account in frame of the nonlocal CR transport theory.Numerical calculations show that CRs scattering and accelerating in other galaxies get a more hard spectrum and for this reason may be available for observation.