THERMOSPHERIC VERTICAL WINDS ABOVE MAWSON, ANTARCTICA

High-resolution (R similar or equal to 200,000) night-time Fabry-Perot spectra of the lambda 630 nm OI thermospheric airglow emission obtain ed from Mawson, Antarctica, during the austral winter of 1992 have bee n used to provide estimates of thermospheric temperature and neutral w ind. In this paper, we report on characteristics of the resulting vert ical wind estimates. The final data set comprised 103 observing nights between 18 March and 20 September for a total of 2096 useable zenith spectra. Because the instrumental reference rest wavelength of the lam bda 630 nm emission is not known, this experiment was only capable of measuring vertical wind Variations relative to an arbitrarily-chosen r eference velocity. For this work, we established our reference by requ iring that the nightly mean vertical wind be zero. We have divided our data into two subsets, corresponding to days of quiet and moderately disturbed magnetic activity. In both cases, the mean dairy variation i n vertical wind velocity was dominated by its diurnal component with d ownward winds (relative to our chosen zero, and negative) appearing pr ior to local magnetic midnight and upward (positive) winds after. Aver aged over all days of low magnetic activity, the diurnal range was -2. 6 to 3.0m s(-1), whilst for days of moderate activity, it was -6.8 to 4.1 m s(-1). Superimposed on this mean vertical wind are fluctuations at shorter periods than our sampling interval of 1 h. We estimate the distributions of vertical velocities prevailing during our observation s to be characterized by one-sigma halfwidths of 14.3 and 18.7 m s(-1) for low and moderate magnetic activity, respectively. This experiment has yielded generally smaller estimates of vertical wind speeds than those;reported by previous authors from auroral latitudes for similar levels of magnetic activity. Comparison is also made with the UCL ther mospheric general circulation model.