The presence of heavy particles in cosmic rays makes it plausible that cosmic radiation is generated by the acceleration of charged particles in extended electromagnetic fields. The energy density of cosmic rays ($3\times {10}^{-10\mathrm{}}\frac{M{c}^2}{{\mathrm{cm}}^3}$) would lead to very great total amounts of energy if one assumes that cosmic radiation extends throughout intergalactic or throughout interstellar space. This would require very efficient methods of cosmic-ray production. It is therefore of interest to investigate the possibility that cosmic rays are generated in the vicinity of the sun and are confined to the solar system by extended magnetic fields. The strength of these fields is estimated to be ${10}^{-5\mathrm{}}$ gauss. According to this picture, cosmic rays circulate in the neighborhood of the planetary system for thousands of years, during which time the radiation becomes isotropic. The electron component of the radiation is eliminated by collisions with solar light quanta.

• Received 27 January 1949

DOI:https://doi.org/10.1103/PhysRev.75.1729