A detailed investigation using interplanetary magnetic field measurements and particle data from ground-based neutron monitors, lunar sensors, and satellite-borne detectors has been made of the marked increase in cosmic ray intensity early on August 5, 1972. This enhancement was observed over the wide energy range 0.5 MeV to ~1 GeV and occurred during the recovery from the greatest recorded Forbush decrease. The increase at ~0300 UT on August 5 was in approximate coincidence with a decrease from ~40 to ~10 &ggr; in the interplanetary field intensity and a change in the field direction from approximately radially outward to approximately radially inward. Sharp decreases in all particle fluxes occurred at about 0500 UT coincident with the increase in interplanetary magnetic field intensity from ~20 to ~40&ggr; and a change in the field direction to radially outward. A detailed analysis of the neutron monitor data shows that the enhanced (~1 GeV) particle fluxes were not of solar origin. It is suggested that the enhancement occurs in a low-intensity interplanetary magnetic field bounded by tangential discontinuities, which connects to different particle sources both near the sun and in the outer solar system. The width of the regime was ~3¿106 km and resembled a magnetic well convected past the magnetosphere. The similarities in the structure of the event as observed by different detectors, the changes in the helium to proton ratios, the time delay of ~9 min between observations at Explorer 41 and those at the moon, and a north-south asymmetry in the enhancement observed by the neutron monitors are all explained in terms of this model.