The disappearance of equatorial E s and the reversal of electrojet current

Based on simultaneous observations of the horizontal geomagnetic field component H, sporadic E (E _s ) and E-W electron drifts at stations close to the dip equator within the equatorial electrojet region, it has been found that on quiet days and sometimes on disturbed days, when there is an abnormal large decrease in H during daytime, there is a simultaneous disappearance of E _s and a reversal of the direction of drift of electrons from westward to eastward. This suggests that the disappearance of equatorial E _s during day-time is due to a temporary reversal of the electrojet current, which is caused by the imposition of an additional electrostatic field opposite in direction to that of normal S _a field.