Cosmic Rays in the Disk and Halo of Galaxies
  We give a review of cosmic ray propagation models. It is shown that the
development of the theory of cosmic ray origin leads inevitably to the
conclusion that cosmic ray propagation in the Galaxy is determined by effective
particle scattering, which is described by spatial diffusion. The Galactic Disk
is surrounded by an extended halo, in which cosmic rays are confined before
escaping into intergalactic space. For a long time cosmic ray convective
outflow from the Galaxy (galactic wind) was believed to be insignificant.
However, investigations of hydrodynamic stability and an analysis of ISM
dynamics (including cosmic rays) showed that a galactic wind was emanating near
the disk, and accelerating towards the halo, reaching its maximum velocity far
away from the disk. Therefore convective cosmic ray transport should be
important in galactic halos. Recent analysis of the gamma-ray emissivity in the
Galactic disk of EGRET data, which showed that cosmic rays are more or less
uniformly distributed in the radial direction of the disk, as well as the
interpretation of soft X-ray emission in galactic halos, give convincing
evidence of the existence of a galactic wind in star forming galaxies.
