Magnetic Storms and Cosmic-Ray Intensity

Abstract

DURING February–April 1947, which was a period of pronounced solar activity, we kept, at Lahore, hourly observations of the cosmic-ray intensity during the day-time with the view of studying its possible correlation with changes of magnetic intensity. Cosmic-ray intensity was measured with a triple counting vertical telescope1, the counts per minute being corrected for the pressure and temperature variations obtained from meteorological data. Hourly values of H were obtained from the nearest magnetic observatory at Alibag (Bombay) and are given in terms of gamma (1 I3 = 10â3 gauss). A plot of the mean day-time values determined for the same hours for cosmic-ray and magnetic intensity showed a marked variation of each, during magnetic storms ; but in general over the period of almost two months the correlation coefficient between I and H shows a slight positive tendency, though we find it to be below the statistically significant level. This might possibly be due to the fact that the magnetic changes and cosmic-ray intensity changes at two widely different stations during magnetically quiet or slightly disturbed days may not be correlated, while the changes during strong storms might be observed simultaneously even at different stations, sometimes all over the world2,3.