ON CERTAIN ASPECTS OF DAILY VARIATION OF GEOMAGNETIC-FIELD AT LOW LATITUDES

The daily variations of horizontal component of geomagnetic field, H, at low latitudes show significant asymmetry during active solar years. After reaching a maximum value at or slightly before noon the H field decreases to the nighttime base level rather slowly even after sunset. The effect is present during any of the seasons and at different longitude sectors. The maintenance of current after sunset is observed even in DELTAH Trivandrum minus Alibag. The continuation of positive DELTAH (TRD - ABG) after sunset is more prominent during disturbed than on quiet days. The midday peak of DELTAH at equatorial station occurs later during local winter than during local summer months at different longitudes. The equatorial electrojet current is suggested to be due to combined effects of multitude of sources of electric fields having different daily, seasonal and solar cycle variations.