The three types of cosmic-ray fluctuations and their significance

Abstract

A theory of cosmic-ray bursts is advanced with which the energy released in them is assumed to come not from the cosmic-rays themselves but from the battery which charges the electroscope. These bursts then represent, according to this theory, instrumental accidents which must be eliminated before the remaining fluctuations can be interpreted. The discovery that the remainder of the ionization observed in a cosmic-ray electroscope is due wholly to positrons and negatrons shooting through the chamber makes it possible to compute the fluctuations to be expected from a random distribution of these electron shots. The observed fluctuations, after the elimination of bursts, are found to be somewhat larger than the fluctuations thus computed. From the amount of this excess the percentage of cosmic-ray "showers" (two or more associated tracks) can be computed and is found by Evans and Neher to be in general agreement with the number directly observed in cloud-chamber experiments.