Characteristics of Eight Hour Waves in the Mesosphere and Lower Thermosphere at High Northern Latitudes

Nocturnal measurements of the mesosphere and lower thermosphere from Resolute (74.7N) and Thule Air Base (76.5N) have shown that an eight hour oscillation can at times be the dominant variation in the neutral wind. Typically, the semi-diurnal tide dominates the temporal variations observed in the mesosphere and lower thermosphere at these sites. The amplitude of the semi-diurnal tide is variable and occasionally diminishes to negligible levels: during some of these abatements higher frequency oscillations in the horizontal wind develop with amplitudes comparable to the semi-diurnal tide (on the order of 10 m/sec), linger for several cycles, and then diminish in amplitude. This paper will document several occurrences of the eight hour oscillation observed during the past decade with instrumentation from the Michigan Airglow Observatory Network.