Surname: Venkatraman First Name: Sarita Status= studentno Institution: University of Texas at Dallas E-mail: sarita@utdallas.edu ---------------------------------------- Title: Interhemispheric Flows in the Equatorial Topside Ionosphere ---------------------------------------- Authors: Sarita Venkatraman and Rod A. Heelis ---------------------------------------- Abstract: Latitudinal, longitudinal, and seasonal variations in the field-aligned and perpendicular flows measured at an altitude near 830 km, by the Defense Meteorological Satellite Program (DMSP) F10 satellite are examined. These profiles are studied during the nighttime (2100 MLT) for solstice periods in 1991 when the solar activity is very high. Latitude and longitude variations show the influence of F-region winds in modulating the observed field-aligned flows. At night, large downward field-aligned flows of the order 400-600 m/s are observed in the winter hemisphere and coincide in longitude with the location of previously identified adiabatic heating effects studied by Venkatraman and Heelis [1999a]. Interhemispheric flows at 2100 hrs local time are seen to extend up to apex heights of about 1000 km during times of high solar activity. Perpendicular drifts however, are relatively invariant with latitude as expected. The ability to combine latitude profiles of the ionospheric temperature, composition, and velocities at specific longitude and local time and comparing these to the available wind data, enables us to quantify the wind influence on the topside ionosphere and its role in affecting the interhemispheric transport of plasma across the equator. An extensive database of of nighttime F-region winds from Arequipa, South America, are also analyzed in the presented work. By comparing the daily variations in the topside with those seen in the F-region winds, we can uncover those changes that may be attributed directly to neutral winds. ---------------------------------------- Discipline Category: Ionosphere Discipline Category: Topside Ionosphere