Balloon study of high-altitude radiations during the international geophysical year

Abstract

The results of a series of 85 constant level balloon flights conducted during the IGY period to measure cosmic rays and other types of radiation at high altitude are summarized. Each flight carried an ionization chamber, a Geiger counter, and nuclear emulsions, and remained at approximately 10 g/cm2 depth for times between 2 and 24 hours. The majority of flights were made at Minneapolis, Minnesota. The large decrease in primary cosmic-ray intensity between 1956 and 1958 was observed at high altitude. The high-altitude measurements correlate with sea-level neutron instruments. Many special events were detected, including X rays produced by electrons incident on the atmosphere during strong aurorae and solar cosmic rays detected on ten occasions and correlating with other known observations made in the polar regions. In one case γ rays originating on the solar surface were detected in a short burst. Several cases of radioactive layers in the atmosphere at low level resulting from nuclear explosions were found. This paper summarizes the entire program, and gives the instrumental details, a summary of published information, and detailed analysis of many data not heretofore published.