Pc 5 Pulsations in the Equatorial Region of India

The properties of Pc 5 pulsations at Choutuppal (Geomag. Lat.: 7°.5N) near Hyderabad, observed over a period of 10 years from 1967 to 1976, are presented. Some of the features observed are: (a) a pre-noon maximum in the diurnal occurrence pattern, as also in amplitude variation (b) decrease of Pc 5 period around the dawn hours. The influence of the level of magnetic activity on different features of Pc 5 pulsations is reflected in (i) the maximisation of Pc 5 activity at higher values of Kp and (ii) an increase in amplitude and a decrease in period with increase in Kp. The long range solar cycle effects on Pc 5 occurrence and period over these 10 years, involving a major portion of Solar Cycle No. 20, presents some interesting features, (i) a double peak in the Pc 5 occurrence—one corresponding to the sunspot maximum interval 1969-70 and the other coinciding with the geomagnetic activity maximum in 1974, (ii) occurrence of shorter periods during sunspot maximum year and longer periods during minimum year. The results from this station, located in the equatorial zone, are discussed in relation to other observational reports and the existing theories on Pc 5 generation mechanism.