Anhalysis of density measurements from the AE-E satellite have demonstrated that the local time variation in the thermosphere at low latitudes (<20¿) changes from predominantly semidiurnal at low altitudes (~140 km). this behavior is significant because it both affects the accuracy of density predictions at low satellite altitudes and confirms that the mesospheric semidiurnal tide is important to the dynamics of the lower thermosphere. Comparison of the results with the local time dependence found in the thermospheric model of Jacchia (1971) and the MSIS model of Hedin et al. (1977a and b) indicate that only the latter correctly models the transition to dominantly semidiurnal behavior at lower thermospheric altitudes near the equator.