Characteristics of the Van Allen radiation zones as measured by the scintillation counter on Explorer VI

A scintillation counter responding principally to direct electrons has been flown on the Explorer VI earth satellite in an elliptical orbit extending to 48,600 km. The instrument measured fluxes of electrons above 200 kev and protons above 2 Mev. After a week of magnetically quiet observations, a geomagnetic storm occurred, and an immediate increase in the counting rate of this instrument was detected; other radiation instruments showed a decrease in counting rate at this time. Gross fluctuations in particle intensity were observed at the edge of the outer zone of the Van Allen radiation belt during the storm, and these fluctuations are closely related to simultaneous geomagnetic activity. The increased particle intensity in the outer zone declined quite slowly after the storm until the next period of magnetic activity about two weeks later. This paper presents a detailed summary of the observations made by the scintillation counter during the period of data reception from the satellite.