Observations of primary cosmic-ray variations using ion chamber and Geiger counters: 1. A comparison of the long-term and Forbush variations

Measurements of cosmic-ray intensity made by an ion chamber and a Geiger counter on balloon flights over Minneapolis during 1959–1963 are presented. The cosmic-ray intensity is shown to be uniquely related to the neutron monitor rate at high latitudes and at the equator. Of particular interest are the solar-cycle modulation and the individual Forbush decreases, seven of which were registered at different levels of the cosmic-ray intensity. It is found that the effects of the two modulations, when studied over identical levels of cosmic-ray intensity, are identical within the accuracy of our method of comparison.