Pi2 Pulsations in the Indian Equatorial Region

Abstract

Well-defined waveforms and the dominance of <i>H</i>_x component are the general characteristic features of the Pi2 pulsations in the equatorial regions. The present study, besides bringing out these features, also indicates some specific differences between the events appearing at widely separated stations in the Indian equatorial region. The study entails a comparison of Pi2 events recorded at the two stations, Choutuppal (geomag. lat.; 7 .5) and Etaiyapuram (geomag. lat.; - 0 .6) during 1976, the data being restricted to the events that occurred during nighttime (1800-0600 hrs LT). It is seen that the Pi2 signals at Etaiyapurarn, while maintaining close resemblance in the waveform and periods to those appearing at Choutuppal, however, show: (i) decreased amplitudes in the <i>H</i>_x component and (ii) enhancement of amplitudes in the <i>H</i>_y and <i>Z</i> components. Also, while the polarization vector at Choutuppal is mainly N-S oriented, it shows a tendency to swing towards NW at Etaiyapuram. The results are suggestive of induction effects due to a subsurface conductivity anomaly in the neighbourhood of Etaiyapuram besides possible effects due to nearby coast.