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Abstract:
A number of minor geomagnetic storms were observed during the period of 21-25 December 2014, and we identified anomalous magnitudes and polarities of the electric field perturbations over the equatorial F region in the Indian sector on many occasions. In this work, we focus on the post-midnight space weather-induced electric field perturbations. These electric field perturbations are inferred based on the variations in the night-time vertical drifts over the Indian dip equatorial station, Tirunelveli (8.7 N, 77.7 E, dip angle 1.7). The post-midnight vertical drift variations over Tirunelveli on 21 and 23 December 2014 suggest the influence of overshielding electric field. However, larger vertical drifts are noticed when magnitude of the overshielding effect is less and vice-versa. These anomalous behaviors in the equatorial vertical drift are shown to be due to the additional effects of substorm, IMF By and disturbance dynamo. This result is important as it suggests influence of the multiple space weather drivers acting in tandem to determine the magnitude and polarity of the disturbance electric field over the dip equatorial ionosphere. This result will be discussed in detail.
