Balloon measurements of cosmic ray protons and helium over half a solar cycle 1965-1969

Abstract

Differential energy spectra for protons and helium covering the energy range 100–260 Mev/nucleon were obtained from balloon flights made each summer (1965–1969) at Churchill, Manitoba, with the aid of a Geiger-tube hodoscope operated in conjunction with two scintillation elements used to measure (dE/dx) and E. Supplementary data from balloon flights at Minneapolis, Minnesota, and Sioux Falls, South Dakota, and from calibration exposures to protons and electrons were used to define backgrounds and to verify the predicted detector response. The observed proton spectra are characterized over a wide range of energy (30–300 Mev) by a simple relationship between cosmic-ray intensity J and kinetic energy T:J = AT. The helium spectra also follow this law at solar maximum but rise less steeply near solar minimum. This characteristic behavior can be interpreted in terms of a simple model in which convection is balanced by adiabatic deceleration.