Cosmic Ray Measurements between Australia and Japan

Abstract

Cosmic ray results obtained on a journey to and fro between Australia and Japan are described. The apparatus was that used previously on the H.M.A.S. Wyatt Earp(l), but since modified, and extended to record showers. A latitude effect of 20 per cent. was found for rays of vertical incidence. The difference between electron and meson components did not exceed the statistical errors of 2 per cent. For wide angle coincidence telescope measurements the latitude effect reduces to 13 per cent. Further it has been found that a latitude effect of some 10 per cent. exists for extensive showers of an average spread of 1 metre. An observed latitude effect of penetrating extensive showers falls, however, within the standard deviation of the measurements. The above results were not corrected for barometric and temperature effects nor for variations in height of the meson-producing layer. Evidence is presented of the existence of a semi-diurnal variation at the equator and at Kure of opposite phase to the barometric pressure variations and of about twice the coefficient of the normal barometric effect. The maximum of the diurnal period occurs at Kure at 2 hours local time and at the equator at 19 hours. A temporary increase of between 2 and 3 per cent. in cosmic rag intensity during the period July 29-31, 1948, is noted.