Recent Faraday rotation (136 MHz) measurements between Ascension Island (8¿ S geographic latitude; 345¿ E geographic longitude; 15¿ S. dip latitude) and the Sirio satellite (azimuth 0¿, elevation 80¿) reveal two characteristic features associated with the undisturbed ambient ionosphere: a late afternoon decrease in TEC followed by a postsunset enhancement that lasts for two to three hours. We theoretically investigate the ambient ionosphere above Ascension Island by numerically solving the time-dependent plasma continuity equation, including the effects of ionization production by solar ultraviolet radiation, loss through charge exchange and transport by diffusion, E¿¿B¿ drift and neutral wind (both zonal and meridional components) appropriate for an equinoctial, solar cycle maximum period. It is found that the postsunset enhancement in upward E¿¿B¿ drift, which is a characteristic feature observed by the Jicamarca incoherent scatter radar facility during solar cycle maximum periods, is primarily responsible for the postsunset increase in TEC observed at Ascension Island between 1900 and 2300 LT. The late afternoon decrease in TEC is caused by an increase in the poleward neutral wind velocity, which lowers the F layer into a higher loss rate region. Inclusion of the meridional wind not only reproduces the observed decrease but also modulates the postsunset peak in TEC so that it is in much better agreement with the observed values. Calculated north-south asymmetries in TEC caused by a zonal wind component are also discussed.