On the relationship between absolute solar cosmic ray intensity and riometer absorption

A study has been made of eight separate solar cosmic ray events that occurred during 1960 using (a) observations above the atmosphere by satellite Explorer 7 of the integral omnidirectional intensity of particles J0 (E > E0), where E0 is 30 Mev for protons and 120 Mev for α particles; and (b) corresponding riometer values of atmospheric absorption A of cosmic radio noise at 27.6 Mc/s from College and Thule stations. The quantities A/J01/2 and J0/A2 are calculated as functions of kinetic energy E for monoenergetic beams of pure protons and pure α particles. Using these results, we show that certain specified ranges of the experimental parameter H(E0) = J0 (E > E0)/A2 for actual solar cosmic ray beams lead uniquely to one of the following conclusions: The atmospheric absorption is due primarily to particles of energy (a) less than E0, (b) approximately equal to E0, or (c) greater than E0. Observed values of H are quite different for different events during 1960, covering the range 40 to less than 10−2 (db2 cm2 sec)−1. During a given event the prevailing tendency is for H to remain approximately constant or to decrease (sometimes markedly) but not to increase with increasing time. It is concluded that atmospheric absorption over the polar caps is often due predominantly to protons of energy less than 30 Mev and/or to α particles of energy less than 120 Mev and that the spectral form in the vicinity of these values of energy varies greatly from event to event and tends to remain about the same or to become steeper (softer) with increasing time during a given event.