COMPARISON OF MODELS AND MEASUREMENTS AT MILLSTONE HILL DURING THE JANUARY 24-26, 1993, MINOR STORM INTERVAL

Results from four first-principle models are compared with Millstone H ill incoherent scatter radar and Fabry-Perot interferometer measuremen ts taken during January 24-26, 1993, a period which included a minor g eomagnetic storm. The models used in this study are the thermosphere i onosphere electrodynamics general circulation model (TIEGCM) with and without forcings from the assimilative mapping of ionospheric electrod ynamics (AMIE) technique, the coupled thermosphere ionosphere model (C TIM), and the field line interhemispheric plasma (FLIP) model. The pre sent study is the first time the AMIE inputs have been used in the TIE GCM model. TIEGCM and CTIM both underestimate the neutral temperature because of an underestimation of the Joule heating rate. An increase i n the high latitude Joule heating would modify the thermospheric circu lation. This could result in increases in N-2 and O-2 density above Mi llstone Hill, which would decrease the AMIE TIEGCM peak electron densi ty (NmF(2)) to agree better with the observations, but would result in poorer agreement between CTIM and the data. The FLIP model NmF is a l ittle low compared to the data, perhaps because of an inadequacy of th e mass spectrometer incoherent scatter (MSIS) 86 model composition or the H+ flux in the model. Good agreement is obtained between atomic ox ygen density [O] given by MSIS and [O] obtained from the radar data us ing a heat balance equation, provided an O+-O collision frequency fact or of 1.3 is used. While the TIEGCM underestimates the electron and io n temperatures, the FLIP model reproduces major features of the data, apart from a large nighttime enhancement in T-e. During the minor stor m interval the observed neutral winds show alternating equatorward sur ges and abatements apparently due to passage of traveling atmospheric disturbances (TADs) seen in the model results. These are associated wi th a late evening increase observed in NmF(2) accompanied by a large i ncrease in F-2 peak height (hmF(2)). These perturbations in NmF(2) and hmF(2) are not reproduced by the TIEGCM or CTIM. The NmF2 increase ma y be due to a decrease in O+ recombination rate caused by the higher h mF(2), combined with compressional effects of a TAD and an enhanced do wnward flux of O+ ions.