OBSERVATIONS OF THERMOSPHERIC HORIZONTAL NEUTRAL WINDS AT WATSON LAKE, YUKON-TERRITORY (A=65-DEGREES-N)

Fabry-Perot interferometer observations of the thermospheric O I (6300 Angstrom) emission have been conducted from an airglow observatory at a dark field site in the southeastern Yukon Territory, Canada, for th e period November 1991 to April 1993. The experiment, operated in an u nattended, remote fashion, has resulted in a substantial data set from which mean neutral winds have been determined. Dependent upon geomagn etic activity, the nocturnal location of the site is either equatorwar d of the auroral oval or within the oval boundaries. The data set is r ich enough to permit hourly binning of neutral winds based upon the K- p geomagnetic disturbance index as well as the season. For cases of lo w geomagnetic activity the averaged, vector horizontal neutral wind ex hibits the characteristics of a midlatitude site displaying antisunwar d pressure-gradient-driven winds. As the geomagnetic activity rises th e late afternoon and evening winds slowly rotate sunward in an anticlo ckwise direction, initially remaining near 100 m/s in speed but eventu ally increasing to 300 K-p > 5. For the higher levels of activity the observed neutral wind flow pattern resembles a higher-latitude polar c ap pattern characterized by ion drag forcing of thermospheric neutral gases. In addition, rotational Coriolis forcing on the dusk side enhan ces the ion drag forcing, resulting in dusk winds which trace out the clockwise dusk cell plasma flow. On the dawn side the neutral winds al so rotate in an anticlockwise direction as the strength of geomagnetic disturbances increase. Since the site is located at a transition lati tude between the midlatitude and the polar cap, the data set provides a sensitive test for general circulation models which attempt to param eterize the contribution of magnetospheric processes. A comparison wit h the vector spherical harmonic (VSH) model indicates several regions of poor correspondence for December solstice conditions but reasonable agreement for the vernal equinox.