Energy Dependence of Transient Changes in the Primary Cosmic-Ray Spectrum

Abstract

Quantitative comparisons are made between the cosmic-ray intensity variations observed by a Geiger counter telescope and ionization chamber at a high geomagnetic latitude, high latitude neutron monitors at sea level, and at two different mountain altitudes, Geiger counter telescopes situated 40 meters of water equivalent underground, and a neutron monitor and Geiger counter telescopes at a low geomagnetic latitude. Long-term and short-term variations are considered. As the intensity variations were large, and as the instruments were all of good statistical accuracy, considerable reliance can be placed in the determinations. It is shown that similar comparisons published by other investigators are in agreement with these determinations, provided adequate allowance is made for the altitudes at which the data were obtained. Writing the differential energy spectrum of the primary cosmic radiation as $j(E)$, and measuring $E$ in Bev, the inter-instrument comparisons are used to show that the average spectral changes approximate to the law $\ensuremath{\delta}j(E)=\mathrm{const}{(1+E)}^{\ensuremath{-}\ensuremath{\beta}}j(E)$; where $\ensuremath{\beta}\ensuremath{\approx}0.9$ for short-term variations, and $\ensuremath{\beta}\ensuremath{\approx}1.2$ for long-term variations.It is shown that the amplitude of the long-term variation is markedly dependent upon altitude. Some evidence is presented that there might be a north-south asymmetry in the long-term variation, the amplitude being greater in southerly directions.