Daily total cosmic ray indices at Huancayo and world geomagnetic indices and magnetic storms

Abstract

The relationship between the time variations of the earth's magnetic field and the corresponding variations in cosmic ray ionization has been looked into by Messerschmidt, by Forbush, by Hess, by Hogg and by Lange and Forbush among others. Striking effects during magnetic storms have been reported but quite a few occasions exist when no such effect could be detected. A method to characterise the cosmic ray values recorded in a day in analogy with magnetic variations at an observatory is given. The cosmic ray indices have been calculated from Lange and Forbush's two hourly mean readings at Huancayo for all days in 1940 and for magnetically disturbed days from June 1936 to December, 1944. The values have been shown against total geomagnetic indices of the world and dot diagrams also plotted. In the daily cosmic ray indices for 1940, the dot diagram does not point definitely to any relation, i. e. the scatter is too broad. In the dot diagram for the disturbed days there is a sort of general increase of world geomagnetic indices and cosmic ray indices. But the increase seems to fall into two branches, one where the cosmic ray index is large and the magnetic index is relatively small and the other where the cosmic ray index is comparatively smaller but the magnetic one seems to dominate. More definite conclusions may be possible if data from other observatories are also analysed.