Where Are Cosmic Ray Pevatrons?
The origin of Galactic cosmic rays is associated with the most energetic astronomical objects in the Galaxy, primarily with the supernova remnants. It is usually assumed that the particle energy about few PeV/Z (1 PeV = 10^15 eV; Z is the particle charge) is the upper limit for acceleration in the majority of supernova remnants. It explains the corresponding break (the knee) in a power law energy spectrum and the changes of elemental composition of cosmic rays above the knee. We discuss how modern theory of particle acceleration by supernova shock waves with the subsequent diffusion in the interstellar magnetic fields is compatible with this scenario and how gamma ray astronomy may demonstrate the existence of Pevatrons in the Galaxy.