Diffusion of protons in the outer radiation belt

The diffusion of protons in the outer radiation belt due to violation of the third adiabatic invariant has been examined. The particular mechanism studied is one in which variations in the intensity of the solar wind produce magnetic disturbances causing motion of particles between L shells. A Fokker-Planck diffusion equation is used with terms describing Coulomb energy degradation and charge-exchange losses with the ambient atmosphere. A source near the magnetopause is assumed. The diffusion constant is numerically evaluated by an analysis of observed frequencies of sudden impulses and commencements. The equation is solved to obtain radial and energy distributions. A comparison of the results with the measured proton fluxes of Davis, Hoffman, and Williamson indicates that a diffusion process of this general nature seems to be responsible for the observed outer-belt protons. For the parameters selected, the magnetic disturbances studied may not be sufficient to produce the required diffusion rate. The effects of possible changes in parameters are discussed.