The physical processes which couple the mid-latitude ionosphere and protonosphere are complicated during the postsunset period when temperatures are rapidly changing. We have studied these processes with incoherent scatter measurements of the electron densities and proton and O+ vertical velocities in the topside ionosphere with 10-min time resolution. Large velocity differences between the H+ and O+ ions in the topside ionosphere occur at times. The two vertical fluxes follow similar temporal trends at high altiudes, where the species have diffusive equilibrium profiles, both of which simply contract after sunset as the ionosphere cools. AT lower altitudes, however, the charge exchange reactions can destroy the similarity in the temporal behavior of the two fluxes and can lead to ion counterstreaming at times. Therefore there is no simple relationship between the F2 region O+ flux and the total ion transport between the ionosphere and the protonsphere.