Cosmic Rays in the Galaxy: Convection or Diffusion?

The theory of the self-trapping of cosmic rays in our Galaxy shows that cosmic-ray particles stream steadily away from their sources at a speed given by that of hydromagnetic waves. Random diffusion along magnetic field lines is a comparatively negligible process. A crucial role in confining high-energy cosmic rays is played by the less dense material on the edges of the galactic disk or in the halo.