Anisotropy of Galactic Cosmic Rays and the Interplanetary Magnetic Field

Abstract

IT has been demonstrated^1,2, using data from high counting rate instruments, that the daily variation of secondary cosmic ray intensity measured on the ground can in general be related on each day to an anisotropy of primary galactic cosmic rays. The anisotropy can vary from day to day in magnitude, in the directions with respect to the Earth–Sun line of maximum intensity T_max and of minimum intensity T_min outside the influence of the geomagnetic field, and in the energy spectrum of variation. T_max and T_min are usually separated by 8–10 h. This has led Rao and Sarabhai to suggest that the anisotropy appears generally to be due to two principal processes, one a modulation equivalent to a pair of oppositely directed positive and negative sources, and the other a negative virtual source approximately oriented along the garden hose direction towards the Sun.