Report on Cosmic-Ray Observations Made on the United States Antarctic Service Expedition, 1939-1941

The program of the cosmic-ray observations is outlined and the results are summarized. The cosmic-ray intensities observed on the voyage of the U. S. M. S. North Star are examined, and it is found that if an external temperature coefficient of -0.15 per cent per degree C. is applied to the data, no increase in cosmic-ray intensity south of 45° geomagnetic latitude is observed. The record of cosmic-ray intensity over the Antarctic winter showed a correlation with upper air temperature somewhat more pronounced than with that at sea-level. Only one of the magnetic storms was found to be followed by a noticeable decrease in the cosmic-ray intensity. The size-distribution of bursts was found to fit the usual exponential relation with an exponent of -2.65. The correlation coefficients between the cosmic-ray intensity, the pressure coefficient, and the temperatures at various levels in the atmosphere are computed, and the significance of each is discussed. The cosmic-ray intensity is found to be a function of upper atmosphere temperatures as well as of that at sea-level.