The primary cosmic-ray electron spectrum in the energy range from 300 MeV to 4 BeV from 1964 to 1966

Abstract

Measurements of the primary electron spectrum were made during the summers of 1964, 1965, and 1966 using a balloon-borne counter telescope flown from Fort Churchill, Manitoba. Several balloon flights were carried out in each year in order to eliminate short-term intensity variations. This paper addresses itself to two questions: (1) the determination of the energy spectrum of primary electrons in the energy interval from 300 MeV to 4 BeV; and (2) the long-term intensity variations of the primary electron flux from 1964 through 1966. The energy spectrum was determined with improved accuracy in 1966 and agrees with our previous results. Comparison of the electron spectra obtained in 1964, 1965, and 1966 shows that, within the errors of our measurements, no long-term intensity variation existed. The upper limit for the change of flux with respect to 1965 amounts to 20% in all energy intervals studied.[Formula: see text]