The variation with time of the flux and energy spectrum of primary cosmic ray alpha particles

Abstract

The total flux and energy spectrum of primary cosmic-ray alpha particles at the top of the atmosphere have, been measured in emulsion stacks flown during September 1956 and June 1958. Values of 240 ± 26 and 130 ± 15 particles/m² storadian second respectively were obtained for the total flux. This reduction in the flux during June 1958 was caused by the partial removal of those alpha particles with energies between 100 and 2000 Mev/nucleon. These changes have been correlated with the 11–year cycle of solar activity.