VARIABILITY OF WINDS AND TEMPERATURES IN THE LOWER THERMOSPHERE

High-resolution daytime incoherent scatter radar measurements of plasma temperatures and drifts in the ionospheric E-region above Millstone Hill (42.6 N, 71.5 W)have been used to derive horizontal neutral winds and temperatures in the lower thermosphere (105-130 km) during five multi-day campaigns in 1987-1991. The underlying semi-diurnal tidal component has been determined from the observations, with characteristic average amplitudes of 50 +/- 15 m/s and 30 +/- 10 K. Phase propagation with altitude follows the expected structure of semi-diurnal tidal modes, but reveals complex coupling of tidal modes, particularly above 11 5 km. Day-to-day variability in the winds and temperatures is large, and the deviations from the semi-diurnal harmonic can exceed 40 m/s and 50 K. No strong correlations have so far been found with geophysical parameters to explain the observed variability.