Role Of Conjugate and Local Terminators On the Electric Fields at Arecibo

Using some recent Plasma drift data at Arecibo, we present evidences of Electric Field (E) changes induced by sunrise and sunset transitions at both local and conjugate regions. Field perpendicular plasma drifts in the F region are used as unambiguous diagnostic of the Electric Field. The large time differences between the local ( 18.35 N, 66.75 W) and conjugate region (46.6 S, 64.7 W) sunrise and sunsets, particularly during the local winter at Arecibo, allow identification of local and conjugate effects on the E field. We present evidences of a downward velocity started around the conjugate sunrise and reaching minimum around the local sunrise, when it turns around and merges with normal daytime behavior, controlled by the dynamo region. During sunset, the upward drift increase at local sunset and shows a dip at the conjugate sunset, when it turns around. Afterwards, the F region is isolated and behaves in regular night time fashion. The entire behavior can be explained by coupled behavior of the E and F region, where the terminator line switches the coupling and affects charge separation at the boundaries. Similar investigations using the summer data have been performed and confirm the interpretation of coupled electric circuit including the local and conjugate regions and intervening ionosphere along the field lines.