Chemistry and Physics Faculty Proceedings, Presentations, Speeches, Lectures

Vertical gradients in the zonal wind observed in the equatorial F-region under postsunset conditions

Event Name/Location

2014 Coupling, Energetics and Dynamics of Atmospheric Regions conference in Seattle, Washington

Date Range

22-26 June 2014

Presentation Date


Document Type



The Guara sounding rocket campaign involved, in part, four sounding rockets that released chemical tracers at different altitudes and latitudes on two consecutive nights in September 1994. Two rockets were launched each night, providing E-region chemical tracer neutral winds at the equator and ~450 km further north, as well as an F-region Barium/Strontium cloud at the equator. The E-region winds were derived at the time, but the Ba/Sr winds were never published due to difficult triangulation conditions. Revisiting the Ba/Sr data has produced a unique dataset showing simultaneous measurements of equatorial neutral winds in the E and F regions, as well as F-region plasma drifts from the ionized Barium. Generally, it is expected that F-region neutral winds begin to reorient eastward as the sun sets, driving an enhancement of the eastward electric field that in turn enhances vertical E x B drifts associated with the onset of equatorial spread-F. However, on both nights, the Ba/Sr observations show strongly westward neutral winds in the F-region, as well as significant vertical shear in the region between 250 and 280 km.