Optical measurements of winds in the lower thermosphere

WAMDII, the wide‐angle Michelson Doppler imaging interferometer, was used to measure the neutral wind in the lower thermosphere by the Doppler shift of the O I 557‐nm line. Observations were made at Saskatoon (60.5° N invariant) around the spring equinox of 1985 with WAMDII coupled to an all‐sky lens. With dopplergrams averaged over 3 to 30 min, no evidence was found for persistent highly localized winds on either of the two nights studied, one viewing only aurora and one viewing only air glow. The nocturnal variation was determined for both nights using average horizontal wind for the whole all‐sky image. The pattern for the auroral case shows winds parallel to the aurora orientation in the evening but substantial crosswinds near midnight. High latitude general circulation models seem to represent this case better than local auroral generation models. The airglow case showed eastward winds in the morning sector.