A large vertical wind in the thermosphere at the auroral oval/polar cap boundary seen simultaneously from Mawson and Davis, Antarctica

Ground-based Fabry-Perot spectrometer observations from the Australian Anta rctic stations of Davis and Mawson show an upward wind greater than or equa l to 100 m s(-1) in the thermosphere at similar to 240 km altitude on the n ight of Day of Year 159 in 1997. The wind was from a region located polewar d 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 similar to 22:00 UT. A s the auroral oval moved northward the region of upward wind followed, and was seen at Mawson (some 4 degrees magnetically north of Davis) just over 1 h later. It is shown that the presence of the large upward wind does, at t imes, 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 observation s before and after the vertical wind event. A lower limit of the area of th e region of upward wind over Mawson and Davis on this night is estimated as similar to 6 x 10(11) m(2). The estimated power required to drive the upwa rd wind over this area at 240 km altitude is of order 6 x 10(9) W. We estim ate that this represents between 3 and 7% of the geomagnetic power input in the southern hemisphere during this interval. (C) 1999 Elsevier Science Lt d. All rights reserved.