Seasonal cosmic-ray effects at sea level

Abstract

By sending a Neher self-recording electroscope in a 10-cm lead shield repeatedly on a slow Norwegian steamer over the route Vancouver-Los Angeles, around South America and return to Los Angeles and Vancouver, we find (1) as heretofore an equatorial dip measured from Los Angeles of seven percent on the western side of South America, eight percent on the eastern side; (2) no measurable seasonal effect, or winter-summer differences, at all in the voyage from Los Angeles to the Straits of Magellan; (3) as heretofore constancy in cosmic-ray intensity in summer and fall, within the limits of uncertainty imposed by fluctuations estimated at not over one percent, on the voyage between Los Angeles and Vancouver; (4) but in winter and spring an increase of as much as two or three percent between Los Angeles and Vancouver. This is interpreted as the atmospheric-temperature effect earlier studied by Hess, Compton, and their respective collaborators.