Longitude Effect of Cosmic Radiation and the Position of the Earth's Magnetic Centre

Abstract

THE theory of the allowed cone of electrically charged primary cosmic rays, developed in a number of recent papers by Lemaitre and Vallarta1, is competent to account for the longitude effect if due regard is paid to the fact that the earth's centre does not coincide with its magnetic centre2. Assuming Schmidt's determination3 of the latter and, with Clay, an exponentially decreasing energy distribution of primary charged particles, it has been shown that the longitude effect along the geomagnetic equator should be roughly sinusoidal with maximum at geographic longitude 12° W. and minimum at 168° E. ; the intensity difference between maximum and minimum is calculated to be about 8 per cent. More recent calculations of the position of the earth's magnetic centre (Bruins4, Bartels5) have somewhat revised Schmidt's earlier result, but the theoretical longitude effect is not much affected thereby. The longitude of the maximum and minimum depends only on the co-ordinates of the earth's magnetic centre, particularly on its longitude ; the intensity difference between the maximum and minimum is closely connected with the distance between the earth's centre and its magnetic centre, to a lesser extent with the energy distribution of primary particles.