The relation between latitude and solar-cycle variations in the neutron-monitor mass-absorption coefficient

Abstract

The differential mass-absorption coefficient for rigidities between 2 and 15 GeV/c for IGY-type neutron monitors at sea level and at 500 mm Hg pressure altitude has been calculated from the variation of the neutron-monitor intensity and mass-absorption coefficient with cutoff rigidity. Combined with six sea-level surveys of neutron-monitor intensity between 1954 and 1962, and assuming no time variation in the neutron-monitor mass-absorption coefficient above 15 GeV/c cutoff, the calculated differential mass-absorption coefficient implies a solar-cycle variation of about 0.04%/mm Hg at 2 GeV/c cutoff rigidity at sea level.