Cosmic Rays and Their Formation of a Galactic Halo.

It is demonstrated that a magnetic gas cloud confined by gravity has no equilibrium configuration if cosmic rays are generated within it. By application of the theorem to the Galaxy, it is shown that cosmic rays lead to inflation of the galactic magnetic fields, producing a halo of cosmic rays and field around the Galaxy. Present observational estimates of cosmic-ray life, magnetic-field strength, etc.,indicate an outward inflation rate of the order of 102 km/sec, although this number may be revised with improved observations. This cosmic-ray halo extends far out from the disk and nucleus of the Galaxy, presumably limited by instabilities which eventually free the cosmic rays and fields at a great distance. The field inflation acts as a pressure regulator on the cosmic rays generated in the galactic disk and nucleus, so that the life of a cosmic-ray particle in the disk of the is determined mainly by the rate of generation of cosmic rays. Present estimates of the cosmic-ray life are based on the rather uncertain value of the density of interstellar gas. The gas is intimately associated both with the dynamics of the galactic fields and the calculated rate of cosmic-ray production.