Summary
Ground-based Fabry-Perot spectrometer observations from the Australian Antarctic stations of Davis and Mawson show an upward wind ~100 m s-1 in the thermosphere at ~240 km altitude on the night of Day of Year 159 in 1997. The wind was from a region located poleward of the poleward edge of the discrete auroral oval, and is identified as a further event of the type seen at Mawson, and elsewhere, in earlier work. The upward wind was first seen over Davis station at ~22 UT. As the auroral oval moved northward the region of upward wind followed, and was seen at Mawson (some 4° magnetically north of Davis) just over 1 hour later. It is shown that the presence of the large upward wind does, at times, affect the horizontal wind inferred from the off-zenith observations. Correcting the affected measurements for the non-zero upward wind leads to a horizontal wind field more consistent with that derived from observations before and after the vertical wind event. A lower limit of the area of the region of upward wind over Mawson and Davis on this night is estimated as ~6 x 1011 m2. The estimated power required to drive the upward wind over this area at 240 km altitude is of order 6 x 109 W. We estimate that this represents between three and seven percent of the geomagnetic power input in the southern hemisphere during this interval.