Dynamics of the lower thermosphere at Saskatoon (52°N, 107°W) during 1988/1989: Comparisons of measurements by a medium frequency radar and a Fabry-Perot interferometer

The Saskatoon medium frequency radar and Fabry-Perot interferometer (FPI) were operated continuously from September 1988 to February 1989. The radar data are from the new phase-coherent system which provides winds from 55/75 to 100/110 km during daylight/night hours. The yield at the airglow layer's height near 97 km is much improved, and regularly provides hourly mean winds even on quiet nights when electron precipitation associated with auroral activity is minimal. Observations of the green atomic oxygen OI 557.7 nm emission provide Doppler winds from the airglow layer, on the relatively few nights per month (2–5) when there is no contamination due to clouds, moon or aurorae. These data are supplemented with winds from the F-region's red atomic oxygen OI 630.0 nm emission, which are referred to on disturbed nights. Comparisons are made between the wind vectors from both systems on individual days (mainly quiet ones), and the resulting tidal profiles/points from the radar/FPI systems. Generally the agreement is excellent, with solar tides dominating the wind field of both instruments. However, on disturbed nights, while the radar winds show little or no change compared to the quiet neighbouring days, the FPI winds (558 nm) demonstrate non-tidal motions quite similar to those obtained from the 630-nm emission.