The Radiation Belts, Natural and Artificial

Data on the time- and space-dependence of trapped particles in three categories were obtained by detectors on the Explorer XV satellite. An unexpected secondary peak in the distribution of high-energy protons was found. The fluxes of high-energy protons slowly increased with time but apparently were not affected by geomagnetic events that caused perturbation of the electron fluxes on the same lines of force. About 1 or 2% of the electrons generated by the nuclear detonation of July 9, 1962 were found to be present in the geomagnetic field 125 days later. The electron fluxes in the region between L = 1.25 and 1.65 earth radii varied by less than 35% over the period from day 110 to day 206 after the detonation of 9 July. The spatial distributions of high- and low-energy electrons are quite different. Electrons in the region above L = 1.7 earth radii are strongly perturbed by magnetic disturbances. A new outer zone of both high- and low-energy electrons was formed by the magnetic storm which began December 18, 1962. (P.C.H.)