The Corpuscular Theory of the Primary Cosmic Radiation

Abstract

The approximately exponential law of cosmic-ray absorption is, at first sight most readily accounted for by the hypothesis that the primaries are composed of photons. However, latitude and asymmetry effects demand that at least 31 percent of the primary radiation be attributed to charged particles. This is enough to spoil the exponential law given so readily by photons unless the charged particle hypothess be developed so as to give an exponential law. The na\"{\i}ve hypothesis that the exponential law is to be provided by a suitable range of penetrations of the incoming rays, resulting from a corresponding range of energy distribution is found untenable, mainly because such a hypothesis would lead to a condition in which the quality of the measured radiation was independent of altitude. The paper reviews a hypothesis already published by the writer to the effect that the primary rays produced secondaries in number per centimeter of path proportional to the primary energy. These secondaries perpetuate the primary path. They represent the rays actually measured, and the theory gives an exact exponential law. The theory gives, in fact, a constant "apparent" coefficient of absorption of the measured effect which is independent of the primary energy. This result requires modification to harmonize with the data on the latitude and directional effects. It is shown that harmonization is provided by a modification of the theory which permits an increase of coefficient of apparent absorption with decrease of primary energy. It is found that such a modification can be readily made in more ways than one. It is then shown that the apparently contradictory phenomenon involved in the "hardening" of the average radiation with passage through matter can readily be accounted for by adding to this hypothesis already made, the known fact of a distribution of energies in the incoming primary corpuscular radiation. A modification of the foregoing theory permits the "apparent" primaries referred to in it to be really photons produced by impact of true primary charged particles with the upper atmosphere. The writer reviews a former hypothesis made by him with regard to the dependence of shower production and atomic burst production in lead, a hypothesis designed to provide an explanation that these phenomena increase with altitude much more rapidly than does the measured cosmic-ray intensity. It results that the extension of the main theory concerned with absorption of the primary energy when combined with the hypothesis concerning burst and shower production results in harmonization of all the details of these phenomena as far as they are known. A list of eleven facts concerned with cosmic-ray absorption, latitude and directional effects, burst and shower production is made. The list comprises all of the outstanding facts concerned with the subject; and it is shown that the extended theory harmonizes all of them.