Roble, Ray

Detailed Modeling of the Global Thermosphere/Ionosphere F-region Structure for the year 2002.

Ionosonde data from 10 stations covering both the high and low latitudes of the Northern and Southern hemisphere were analyzed to determine the global diurnal structure of the ionospheric F-region for the entire year 2002. These data were compared with predictions made by the Thermosphere/Ionosphere/Mesosphere/Electrodynamics General Circulation Model (TIME-GCM) for the same period and same station locations. Good agreement between model predictions and observations were obtained for the overall ionospheric variation for the northern hemisphere stations (Chilton, Moscow, Wallops, Eglin, Wakkanai) but there were discrepancies with the Southern Hemisphere stations (Hobart and Port Stanley). Good overall agreement was obtained at the equatorial stations (Jicamarca, Darwin, Ascension Island). Although the overall structure was well simulated the station variability was not suggesting that atmospheric coupling from the lower atmosphere was stonger than that in the model simulations. The model had tidal, planetary wave and uniform gravity wave forcing at the lower boundary but an additional source of variability of about 50% is needed to match the simulations. The Southern hemisphere discrepancies may be related to the strong planetary wave activity and a major Sudden Stratospheric Warming that occured in the southern polar winter and spring in 2002. These data/model simulations will continue to be studied to determine the coupling between lower and upper atmosphere processes.

This research is a collaborative effort between Henry Rishbeth (Southampton University, England), Michael Mendillo and Joei Wroten (Boston University) and Raymond Roble(HAO,ESSL).