A comparison of the cosmic-ray intensity at high altitudes with the nucleonic component at ground elevation

A series of balloon-borne soundings in the atmosphere with single Geiger tubes has been made during the period January to September 1958. The counting rate determined at the Pfotzer maximum is compared with that recorded by the nucleonic detector at Mt. Washington (1909 m; λ = 55°N). Large changes in the counting rate of each detector were observed, and the ratio of these changes is ∼2 - 1. Several large deviations from this normal ratio were also observed; they occur for flights on which the shape of the intensity-altitude curve near the Pfotzer maximum is quite different from the normal. The changes are explained either in terms of depressions of the low-energy portion of the cosmic-ray spectrum following marked decreases in the nucleonic component or by the presence of excess low-energy radiation. An anomalous increase of ∼100 per cent observed at high altitudes during one flight is attributed to high-energy X-radiation. It is found that the hemispherical average unidirectional intensity above the atmosphere derived from the counting rate at the Pfotzer maximum has decreased ∼200 per cent from 1954 to 1958 at λ = 53°N, and this change is compared with results at other latitudes.