On Some Features of Pc5 Pulsations at Choutuppal (Hyderabad), India

Abstract

Morphological features of Pc5 pulsations observed in the earth currents at an equatorial station over nearly 6 years show a dominant maximum in the morning in occurrence hours of the pulsation, like at high and middle latitudes, and a much subdued maximum in the evening; a peak near midnight is also seen as reported from auroral zone stations. A semidiurnal variation in the period of the pulsations with a distinct maximum at the hour close to dawn and a minor maximum around dusk is noticed in all the seasons and the year. Similarity of the semidiurnal variation in the periods between the equatorial station and a high latitude station is in conformity with the theoretical models wherein it was suggested that ULF waves can also be observed away from the resonance region as the compressional evanescent mode. Time series analysis of the parameter, occurrence hours per day, indicates significant signal corresponding to solar synodic rotation period for the years 1970-72. Some significant quasi-stationary periodicities in occurrence hours per day are noticed.