Asymmetries in the Forbush decreases of the cosmic radiation: 2. Superimposed intensity variations during a Forbush decrease

Intensity increases or decreases, which are sometimes a strong function of longitude, are frequently found superimposed on the normal behavior of the cosmic-ray intensity during Forbush decreases. A study has been made of these effects utilizing the neutron monitor data from many stations distributed in latitude and longitude. The anisotropies recorded as decreased intensities occurred from the west, and those recorded as increases occurred from the east, of the earth-sun line. These anisotropies were both long and short lived. The long-lived anisotropies shifted westward as time progressed. Besides the anisotropies, superimposed intensity increases occurred at all stations at the same universal time, the magnitudes of which were larger at stations sampling particles from directions east of the earth-sun line at the time of the increase. A qualitative explanation of these observed effects is given in terms of the configuration and the possible instabilities of the plasma cloud.