Eleven Year Variation of Cosmic-Ray Disturbance and Its Relation to Solar and Geomagnetic Activities

Abstract

The daily mean intensity of cosmic rays and geomagnetic horizontal component are measured from the 27-day running average values, and this measure of disturbance is named “variability.” The frequency distribution of variability for both cosmic rays and horizontal component deviate from the normal distribution toward negative, and this character is nearly the same amount for two cases throughout one sunspot cycle from 1936 to 1945.The maximum value of cosmic-ray variability delays from the sunspot maximum. Since the circumstance is nearly similar to that of horizontal component, it may be said that a large number of the cosmic-ray disturbance observed at the sunspot maximum time is due to the phenomena related to the magnetic disturbances.Though there are several evidences which indicate the close relation between cosmic-ray and geomagnetic variability, apparent difference is seen at the period of sunspot minimum. It suggests that there is some kind of magnetic disturbance which is independent of cosmic-ray variation.