Twenty-two-year revolutions in the cosmic-ray diurnal variations

Abstract

It is shown, from the data obtained during three complete sunspot cycles, that the 22-year variation in the phase of the cosmic-ray diurnal wave is associated with the 11-year revolutions of the diurnal vectors. The revolutions alternate in sense every 11 years. In order to interpret these revolutions, two perpendicular cosmic-ray streamings in interplanetary space are assumed. As both streamings undergo 11-year variations in their velocities, an ellipse is traced out by the termini of the annual vectors; the sense of revolution depends on whether the phase difference between the two is positive or negative. If, on the other hand, their periods are 11 and 22 years and if their phases coincide, the locus is a horseshoelike trajectory, which is traced twice by a to-and-fro motion during 22 years. The observed data available at this stage cannot distinguish between these possibilities. As geomagnetic activity also shows different 11-year variations alternately, its relation to the 22-year revolution in the diurnal variations is discussed. The radial flow of the cosmic-ray particles as well as the rigid rotation of the cosmic-ray gas with the sun suggested by Parker may correspond to the two streamings.