Geomagnetically quiet day ionospheric currents over the Indian sector—II. Equatorial electrojet currents

Abstract

With 1986 quiet days data of Indian observatories, the equatorial electrojet (EEJ) has been studied in terms of 8 landmark parameters that reveal the structures of hourly latitudinal profiles of EEJ current from 0700 to 1700 h local time. The landmark distances suggest that near dawn, the EEJ is widest and its centre and focus are most northerly before it contracts towards local noon with its centre and focus moving southwards. The seasonal means of peak current intensity and the total forward current seem to peak earlier when the intensity of EEJ is higher than when it is lower. The seasonal order of EEJ intensity is found not to be the same at all hours of the day. This implies that seasonal variation of EEJ is not semiannual at certain daytime hours. The landmark distances of EEJ current have semi-annual variations with minima in the vernal and autumnal equinoxes and maxima at June and December solstices, but annual variations of the measures of EEJ current are just the reverse. Certain properties of the worldwide part of Sq are found to be markedly different from those of EEJ including some key features of diurnal and seasonal variations.