Primary protons and alpha particles in the energy range 70–240 MeV/nucleon observed during 1966

Abstract

The differential energy spectra of cosmic-ray protons and helium nuclei were measured on two balloon flights from Fort Churchill, Canada, during late July and early August of 1966. The measurements were made using a double dE/dx vs. E detector with an energy-independent (for stopping particles) acceptance aperture of 6 cm2 sr. The detector floated for a total of 25 hours under 2.7 g/cm2 of residual material. The acceptance range of energies is 70–240 MeV/nucleon for protons and 4He. Both the proton and 4He differential spectra are depressed from solar minimum and appear similar to 1963 results. The P/He ratio over the energy range is 4.3 ± 1. The spectra are compared to those obtained in 1965. It is found that the modulation function is proportional to either R or Rβ.