Geomagnetic Storm Effects on Ionospheric Drifts & the Equatorial E_s, over the Magnetic Equator

Abstract

Study of the ionospheric drifts at Thumba near the magnetic equator during the geomagnetic storms shows that there are day-time counter electrojets on several occasions, showing eastward electron drift and E_s-q disappearance. Such counter electrojet events are seen for a duration when the geomagnetic <i>H </i>value drops below the night level. This can be checked from the parameter H_equator (at either Trivandrum or Kodaikanal) minus _Hnon-equator (Alibag)] rather than from the simple <i>H </i>value or <i>H </i>minus D_st. The E_s-q is unaffected by the geomagnetic disturbances except for the brief periods of counter electrojet when it disappears. The mean midday <i>f</i>_eE^s on disturbed days is lower than on quiet days due to the more frequent disappearances of Es-q during the geomagnetically active periods rather than the reduction of <i>f</i>_eE^s due to geomagnetic activity.