Terrestrial Magnetism and Cosmic Rays

Abstract

IT has been shown by several observers within the last few years that the ionisation caused by cosmic radiation, when reduced to the same barometric pressure, is not constant. In addition to a very small regular diurnal variation, the existence of which has been proved by continuous registration over a period of three years at 2,300 metres above sea-level¹, much larger and irregular variations have been found by different observers (“Schwankungen zweiter Art”, as they were termed by A. Corlin). These are clearly perceivable when, for example, hourly observations of the cosmic ray intensity (or even the daily mean values) are reduced to standard pressure. At the Hafelekar Observatory in the Tyrolean Alps (2,300 m.) the daily average intensities may differ by so much as 0.10J., that is, by 4 per cent (total ionisation with complete lead screen 10 cm. thick on all sides of the apparatus amounting to about 2.80 J.). With apparatus unscreened from above, even larger variations may occur.