Comparison of nighttime zonal neutral winds and equatorial plasma bubble drift velocities over Brazil

We present results from the first extended period of coincident observations of thermospheric zonal neutral winds and equatorial plasma bubble (EPB) zonal drift velocities over northeastern Brazil during the October to December months of 2009 and 2010. The EPB zonal drift velocities are estimated utilizing images of the O I 630.0 nm emissions recorded by a wide-angle imaging system at Cajazeiras. Thermospheric neutral wind estimates are based upon common volume observations made by a bistatic Fabry-Perot interferometer (FPI) experiment using FPIs located at Cajazeiras and Cariri in Brazil observing the Doppler shift of the O I 630.0 nm emission. The results illustrate a similar pattern of nighttime and night-to-night variations in the zonal neutral winds and EPB zonal drift velocities. In general, the geomagnetic zonal neutral winds and the EPB velocities show an excellent agreement illustrating that the F region dynamo is fully developed. However, in the early evening hours the EPB zonal speed is slower than that of the background winds on several occasions. We conclude that this indicates that during the bubble evolution period in the early evening the F region dynamo is not fully activated.