High energy cosmic ray intensity variations associated with the unusual Forbush decrease of 1972

Spectacular temporal cosmic ray variations at relativistic energies were recorded by all groundbased cosmic ray monitors during August 1972, when Forbush decrease (FD) and other associated intensity changes occurred. These included at least two major relativistic solar particle enhancements and three FD events, one of which is the largest observed todate. Large anisotropies in the intensities were also indicated throughout the entire period during these events. From a comparison with the interplanetary plasma and field parameters observed on various spacecrafts during this period, a comprehensive model is presented for the FD in terms of a shock front, containing tangled magnetic fields with large scale tangential discontinuities, sweeping past the earth. (author)