Acceleration of High-Energy Cosmic Rays

The transport and acceleration of galactic cosmic rays is discussed with emphasis on the highest energies. The mechanism of diffusive shock acceleration is shown to produce a near-universal spectrum which can account for most observed cosmic rays. A quasi-perpendicular shock in general accelerates particles faster and to higher energies than a comparable quasi-parallel shock. Application of these ideas to supernova blast waves suggests that they can produce galactic cosmic rays to the knee in the spectrum, some 3 ×10 15 eV. A similar blast wave, recently identified near the galactic center could accelerate particles to an energy of some 10 18 Z eV or higher (hereinafter Z is the charge in units of the elementary charge). It is possible that the highest-energy cosmic rays could come from the galactic center. If this is the case, there should be an enhancement of the flux of high-energy cosmic rays coming from the galactic center.