CXXXIV. The 27-day recurrence tendency of cosmic ray intensity

Abstract
The 2 7-day recurrence tendency of the cosmic ray intensity has been studied for the nucleon, meson and electron components of the cosmic radiation and the amplitude of the variation is found to be greater for the nucleon component, furthermore the changes in cosmic ray intensity seem to precede those of magnetic activity by 4 or 5 days. The 27-day period corresponds to the time of rotation of the sun and this would seem to indicate that the cosmic ray intensity changes are associated with solar disturbances which, after a delay of several days, produce magnetic storms. There is some evidence to show that the recurrence tendency is due to decreases in intensity which occurat 27-day intervals.