Lower-Thermospheric Winds at High Latitude

Observations made of the high-latitude E-region with the Chatanika, Alaska (65° N), incoherent scatter radar facility during the summer months of 1976 to 1982 are presented. Fourteen 24-h experiments were performed with altitude resolution between 9 and 24 km. Ion drifts measured during these experiments have been analysed to obtain neutral winds at lower-thermospheric heights. Tidal oscillations are the predominant feature of the neutral winds from 90 to 125 km. The semidiurnal oscillation is particularly strong, attaining peak amplitudes of ≈50 m/s at 110 km. Average semidiurnal tidal phases are in good agreement with previous mid- to hight-latitude observations. Average neutral winds are determined for three different levels of geomagnetic activity. During geomagnetically active experiments, the average neutral wind circulation pattern was altered from its normal quiet time behavior above 100 kam. The changes observed in the neutral winds are generally consistent with the predictions of the National Center for Atmospheric Research (NCAR) Thermospheric General Circulation Model (TGCM) for different levels of steady-state magnetosperhic input that reflect increasing levels of geomagnetic activity