FABRY-PEROT SPECTROMETER OBSERVATIONS OF THE AURORAL OVAL POLAR CAP BOUNDARY ABOVE MAWSON, ANTARCTICA/

Zenith observations of the oxygen lambda 630 nm auroral/airglow emissi on (produced at an altitude of similar to 220 to similar to 250 km) we re obtained with the Mawson Fabry-Perot Spectrometer (FPS) during thre e 'zenith direction only' observing campaigns in 1993. The data show m any instances of strong (50 to 100 m s(-1)) upwellings in the vertical wind, when the auroral oval is located equatorward of the zenith. Our data appear consistent with the existence of a region of upwelling up to similar to 4 degrees poleward of the poleward boundary of the visi ble auroral oval, rather than short duration, explosive heating events . The upwellings are probably the vertical component of wind shear pro duced by reversal of the zonal thermospheric winds, which occurs near the poleward boundary of the visible auroral oval. Zenith temperature was also seen to increase when the oval was equatorward of Mawson, sho wing rises of up to 300 K or more. However, this increase is at times unrelated to the upwellings, and seems to be caused by the expansion o f the warm polar cap over the observing site. On a number of nights th e boundary between the polar cap and the auroral oval was observed to pass over our site several times, occasionally showing a quasi-periodi c expansion and contraction. We speculate that this quasi-periodic mov ement may be related to periodic auroral activity that is known to gen erate large-scale gravity waves. Copyright (C) 1996 Elsevier Science L td