EQUATORIAL IONOSPHERIC VERTICAL PLASMA DRIFT MODEL OVER THE BRAZILIANREGION

Comparison between equatorial inospheric F region vertical plasma drif t from satellite measurements [Fejer et al., 1995], for the Brazilian longitude sector, and the drifts derived from ionosonde measurements a round sunset shows significant differences on the prereversal peak beh avior during solstices of high solar activity periods. Using ionosonde measurements around sunset and satellite measurements at other local times, we constructed an ionospheric vertical plasma drift model that is representative of the equatorial region over the Brazilian longitud es, where the magnetic declination is around -20 degrees, The so deriv ed drift model, here called IDM (ionosonde drift model), is used as an input to the Sheffield University plasmasphere-ionosphere model (SUPI M). It is shown that the F layer heights given by SUPIM with IDM are i n good agreement with ionosonde measurements over tile Brazilian longi tudes and that IDM better simulates the F layer heights than the avera ged drifts given by the satellite drift model [Fejer et al., 1995].