The Effect of Atmospheric Tides on the Morphology of the Quiet-Time, Post-Sunset Equatorial Ionospheric Anomaly S. England An understanding of the coupling of heat and momentum sources in the troposphere and stratosphere to regions of the upper atmosphere and ionosphere is important for understanding the near-Earth space environment. Atmospheric tides are directly driven by absorption of solar energy throughout the entire atmosphere, but have major forcing terms in the lower atmosphere coming from processes such as convective heating and latent heat release by large-scale weather systems. The effects of these tides on airglow emissions in the mesosphere and lower thermosphere have been widely observed and many of their features have been well explained. Here, we present observations of a strong influence of atmospheric tides on the density and distribution of F-region ionospheric plasma at low latitudes during equinox, using observations from the TIMED GUVI and IMAGE FUV instruments during Spring 2002. These observations reveal the longitudinal and local time distribution of plasma in this region. Comparisons between these observations and the GSWM tidal model suggest a control of atmospheric tides originating in the lower atmosphere on the development of the F-region ionosphere during the daytime. These observations indicate an unexpectedly strong connection between conditions in the lower-atmosphere and the near-Earth space environment, signalling an important new view of space weather. _______________ Global Aspects of Magnetosphere-Ionosphere Coupling, 2006 Yosemite Workshop, Yosemite National Park, CA, USA, 7-10 February 2006