Disturbance diurnal electric field in Indian and American equatorial electrojet regions

Abstract

The yearly mean Disturbance Daily (SD) variation, i.e., solar daily variation on International Disturbed days (Sd) minus that on International Quiet days (Sq) of the geomagnetic H field at Huancayo, an equatorial electrojet station in American zone, for any of the years 1954-61 shows a dawn-maximum and a dusk-minimum as observed at any low and middle latitude station. Contrary to this, the SD(H) variation at Kodaikanal, an equatorial station in the Indian zone, shows a prominent minimum around noon hours besides the usual dawn-maximum and dusk-minimum for any of these years. The amplitude of SD(H) at Huancayo or at Kodaikanal decreases with the decreasing solar activity. Seasonally, SD(H) is larger during equinoctial than during solsticial months. For any particular season, the SD(H) averaged for all hours of the day is lower at Huancayo than at Kodaikanal, while the Sq(H) at Huancayo is always greater than the corresponding amplitude of Sq(H) at Kodaikanal. Thus the sources of electrojet electric fields on quiet and on disturbed days seem to be different and need to be identified.