A real-time model-observation comparison of F-2 peak electron densities during the Upper Atmospheric Research Collaboratory campaign of October 1997

The first-principles, time-dependent Thermosphere-Ionosphere Nested Grid (T ING) Model has been run automatically in real time to support the Upper Atm ospheric Research Collaboratory (UARC) campaigns. This real-time modeling c apability is the first published description of the running of a comprehens ive model of the coupled thermosphere-ionosphere system that successfully p erforms real-time nowcasts and short-term forecasts of the upper atmosphere . These nowcasts and forecasts use observed real-time geophysical parameter s as model input. Real-time modeling also provides an opportunity to evalua te rigorously the accuracy of the model for space weather purposes by compa ring model outputs with observations. Digisonde-derived F-2 peak electron d ensities from three sites (Millstone Hill, Tromso, and Sondre Stromfjord) w ere compared with the corresponding TING model outputs during the October 1 4-29, 1997, UARC campaign. It is found that under solar minimum, equinox, g eomagnetically quiet conditions, the F-2 peak electron densities simulated by the model were in good agreement with those observed by the Digisondes. At both midlatitudes and high latitudes the TING Model almost reproduced th e observed diurnal variations of F-2 peak electron densities. There were, h owever, short-period variations of F-2 peak electron densities during both day and night that were not simulated by the model.