On World-Wide Changes in Cosmic-Ray Intensity

Abstract

Continuous cosmic-ray records for periods of 17 months or more obtained by Compton-Bennett meters at Cheltenham (United States), Teoloyucan (Mexico), Christchurch (New Zealand), and Huancayo (Peru) are reduced to a constant barometric pressure at each station. After deducting a 12-month wave from the data at each of these stations except at Huancayo, where none is found, a high correlation ($rė0.90$) is obtained between the means of cosmic-ray intensity for each one-third month for any two of the four stations. This high correlation, based on all available data for each pair of stations, is definite evidence that, except for the 12-month waves, the major changes in cosmic-ray intensity are world-wide. With published data from a Steinke instrument on the Hafelekar, near Innsbruck, the world-wide changes, when expressed in percent of the absolute intensity at each station, are found to increase rapidly with altitude for stations at the same latitude. A large increase in the world-wide effect for stations at high altitudes occurs between the equator and geomagnetic latitude 30° north, while no further very large increase occurs up to latitude 47° north. Results for Christchurch and Cheltenham indicate that the magnitude of the world-wide effect is symmetrical about the equator, and its connection with effects observed during certain magnetic storms is discussed. The amplitude of the 12-month wave, which in the Northern Hemisphere has its maximum near mid-January, increases from zero at the equator to about 1.0 percent at Teoloyucan, 1.6 percent at Cheltenham, and 1.9 percent on the Hafelekar. At Christchurch, its maximum occurs near the end of July, its amplitude being about 0.8 percent of the total intensity. Accordingly, it seems that the 12-month wave may not be ascribed to a solar-magnetic moment.