Remarks on the Latitude Effect of Cosmic Rays at Sea-Level

Abstract

During a recent voyage from Australia to Japan the intensity of cosmic rays was measured with several Geiger counter telescopes of different designs. The conclusions to be drawn from these and other results are presented in this paper. It is shown that the latitude effect at sea-level (averaged over all azimuths) is approximately proportional to cos2 1.2ζ, where ζ is the zenith angle of the incident radiation, and that the vertical latitude effect is 18 per cent. In general, the latitude effect depends both on zenith angle and azimuth. The phenomenological relationships of these intensity variations with the zenith angle distribution at two fixed locations, i.e. at high latitudes and at the equator, and with the east-west effect at the equator, are deduced. After correction for longitude and zenith angle, Geiger counter telescope and ionization measurements do not differ by more than their errors of measurements ; the average specific ionization does not vary with latitude. Qualitative explanations of the equality of the latitude effects for mesons and for electrons, as well as of the latitude effect of small extensive showers are given.