The energy spectrum of cosmic-ray heavy nuclei of chargeZ≥10 during a solar quiet time in July 1961

Abstract

The energy spectrum of heavy nuclei (charge Z≥10) has been determined, in the energy interval from 200–700 Mev/nucleon, using a stack of nuclear emulsions, exposed on July 8, 1961, at a mean altitude of ∼2.4 g/cm2 of residual atmospheric depth on a balloon flown from Fort Churchill, Manitoba. The flight was preceded by a period of three months of low solar and geophysical activity. The charge and energy spectra were obtained principally from tracks of particles that ended in the detector by a combination of range and δ-ray density measurements. A second charge estimation for particles that stop in the emulsion was made from integral δ-ray counts as a function of range. The energy spectrum was measured up to 700 Mev/nucleon by also taking into consideration the tracks that pass through or interact within the stack using a combination of δ-ray density and multiple scattering measurements that determine the charge and energy of the nuclei. This energy spectrum was combined with the spectra measured for protons and helium nuclei in the same flight and with similar data obtained during 1963 with a view of arriving at a better understanding on the propagation of cosmic-ray nuclei in source regions, instellar space, and solar system.