During geomagnetic disturbed periods, the q type of sporadic E layer near the dip equator is shown to disappear with maximum error of five minutes during the period when the difference of the geomagnetic H field between the equatorial and non-equatorial station decreases below the night level. These periods are identified with the reversal to westawrd direction of the electrojet currents at the base of the E region around 100 km level irrespective of the changes in the Sq current system which might be produced by the disturbance.