HALE-CYCLE EFFECTS IN COSMIC-RAY INTENSITY DURING THE LAST 4 CYCLES

Monthly cosmic-ray data from Inuvik (0.16 GV) and Climax (2.96 GV) Neu tron Monitor stations has been studied with the aid of solar activity parameters for the time period 1947-1995. Systematic differences in th e overall shape of successive 11-year modulation cycles and similariti es in the alternate 11-year cycles seem to be related to the polarity reversals of the polar magnetic field of the Sun. This suggests a poss ible effectiveness of the Hale cycle during even and odd solar activit y cycles. Our results can be understood in terms of open and closed mo dels of the heliosphere. Positive north pole of the Sun leads to open heliosphere where particles reach the Earth more easily when their acc ess route is by the heliospheric polar regions (even cycles) than when they gain access along the current sheet (odd cycles). In this case a s the route of access becomes longer due to the waviness of the neutra l sheet, the hysteresis effect of cosmic-rays is also longer. This int erpretation is explained in terms of different contributions of convec tion, diffusion and drift mechanisms to the whole modulation process i nfluencing cosmic-ray transport in the heliosphere.