The physical significance of the unusual worldwide fluctuations of cosmic-ray intensity on July 14–15, 1961

We have examined the characteristics of the unusual worldwide fluctuations of cosmic-ray intensity on July 14–15, 1961, using corrected hourly data from global network of neutron and meson detectors. A careful study of the associated solar, interplanetary and geophysical phenomena has also been made. These investigations lead us to recognise the dominant role played by the Interplanetary Magnetic Field Inhomogeneities (IMFI) in modulating galactic cosmic-ray flux received at earth during recovery from Forbush decreases. When approaching the earth from the sunward side the IMFI's scatter galactic cosmic rays diffusing towards solar equatorial plane from higher heliolatitudes on to the interplanetary magnetic-field lines which connect to earth. When propagating past the orbit of the earth, the IMFI's set up a flow of scattered galactic cosmic-ray flux in the general direction of the earth. Most of these cosmic rays probably sink in the sun. Transient Spatial Anisotropies are thus set up in the vicinity of the earth in cosmic-ray intensity as viewed by ground-based detectors. Depending upon the relative position of the region abounding in IMFI's and the earth, these short-lived anisotropies appear either from sunward or antisun directions. Sometimes the configuration is such as to set up bidirectional anisotropies. Implications of this broad picture are discussed qualitatively.Our analysis also enables us to place constraint on the mechanism responsible for heating the solar corona over active regions, which we feel must be taken into account by all theoretical models on the subject.This research is supported in part by U.S. Air Force Office of Scientific Research under grant AF-AFOSR-319-66. The paper was presented at the Tenth International Conference on Cosmic Rays, Calgary, June 18–29, 1967.Now at the Dept. of Physics and Astronomy, University of New Mexico, Albuquerque, N.M., U.S.A.