SPATIAL STRUCTURE IN THE THERMOSPHERIC HORIZONTAL WIND ABOVE POKER FLAT, ALASKA, DURING SOLAR MINIMUM

A new all-sky imaging, wavelength scanning Fabry-Perot spectrometer wa s used to record high-resolution (R similar or equal to 200, 000) spec tra of the lambda 630 nm thermospheric optical emission above Poker Fl at, Alaska. These spectra were used to derive spatially resolved maps of the horizontal wind vector at approximately 250 km altitude. We des cribe the procedure used to infer vector winds from line-of-sight Dopp ler shifts, along with its limitations. We present the time evolution of the vector wind fields obtained from this method for 6 nights of ob servation. Five of the 6 nights contained periods when we inferred the existence of significant curvature, divergence or shear in the thermo spheric wind across our instrument's similar to 1000 km diameter field of view. The sixth night exhibited little spatial structure and is sh own for comparison. We compare these results with a ''generic'' solar minimum winter time run of the National Center for Atmospheric Researc h's Thermosphere, Ionosphere, and Electrodynamics General Circulation Model. While agreement was good at the start and end of the night, con siderable differences were found in the late evening and midnight sect ors. Some possible origins for these discrepancies are proposed. In pa rticular, we suggest that the F region horizontal wind may be deflecte d by upwelling vertical winds, which are in turn driven by E region he ating in the auroral zone. We note that both the instrument used and o ur high-latitude implementation of the analysis procedure are new expe rimental techniques. Thus the data presented here should be regarded a s preliminary and, if possible, be validated by comparison with result s from other techniques.