F-region nocturnal zonal plasma drift velocities of the brazilian equatorial ionosphere during maximum solar

This study focused on the nocturnal zonal plasma drift velocities of ionosphere (F region) at equatorial latitude regions of the Brazil. The zonal plasma drifts result from equatorial latitude electrodynamics with influences from the E and F region conductivities and neutral wind shears in altitude and latitude. The analysis is interpreted using the simple plasma drift model (Eccles, 1998a,b) and monochromatic digital images of OI630nm emission, which allow direct visualization of ionospheric bubbles. The digital images were obtained by optical imager system operating at São João do Cariri (equatorial geographic latitudes: 7.4ºS; 36.5ºW; 19oS dip latitude) from January to December 2001 (maximum solar activity). In this period, 48 quiet nights ( KP<24o) presented the signature of ionospheric bubbles and the zonal drift velocities were calculated (observational results). The geophysical conditions of each quiet night were considered in equations of the simple plasma drift model in order to obtain the theoretical zonal plasma drift velocities between 18LT and 6LT. The theoretical and observational results were grouped seasonally. The theoretical results showed two humps around 20LT-21LT and 2LT–4LT that were present in observational results.<br>Observational results were smaller (greater) than theoretical results before (after) 22LT-23LT being earlier in the Summer. The discrepancies between the theoretical and observed results apparently were due to<br>the neutral wind magnitudes provided by HWM93 empirical model. The Summer 2001 season presented the theoretical and observed results in better agreement considering the bars of variance.