QUASI-BIDAILY VARIATION OF THE GEOMAGNETIC-FIELD IN THE INDIAN EQUATORIAL ZONE

Quasi-bidaily Variation (BDV) in the geomagnetic field due to equatori al electrojet and planetary Sq currents is clearly detected in the Ind ian equatorial zone. The quasi-stationary signal is stronger in EEJ co mpared, to SQ. Larger amplitude of the BDV in EEJ is confined only to late summer in the northern hemisphere indicative of its clear associa tion with the planetary wave in the mesosphere below. A noticeable cha nge in the BDV amplitude is seen following counter electrojet events. However, no concrete evidence is seen for the anticipated association between the movement of Sq focus caused by mesospheric winds and the B DV in EEJ or Sq.