The upper mesosphere and lower thermosphere of the northern polar cap
was investigated using Fabry-Perot interferometer measurements of the
horizontal wind velocity in the lower thermosphere, meridian scanning
photometer observations of atomic oxygen green line brightness in the
lower thermosphere, and Michelson interferometer records of the infrar
ed MeineI OH bands brightness and rotational temperature in the upper
mesosphere. Tidal airglow oscillations in the absence of local solar h
eating were studied using a superposed epoch analysis of observations
obtained around three new-Moon intervals (November 9-22, 1993, Decembe
r 7-20, 1993, and January 4-17, 1994) in Eureka (80 degrees N). Tidal
harmonics were uncovered with an iterated least chi-squared fit, and t
heir existence in the data tested using a goodness-of-fit probability
against a null hypothesis of no oscillations. No single dominant tide
was found at all times and altitudes of the winter Arctic upper mesosp
here and lower thermosphere. The horizontal wind velocity of the lower
thermosphere exhibited all the first three harmonics of the tide, wit
h the largest-amplitude oscillations shown by the diurnal component of
the meridional wave speed. The atmospheric layer near the mesopause t
hat contributes to the OH airglow emission experienced terdiurnal osci
llations throughout the winter season. Theoretical polarization relati
ons for evanescent tides, considerations of energy density propagation
with altitude, and a day-by-day analysis of the zonal and meridional
wind speed and temperature all indicate that the terdiurnal tide obser
ved on November was an evanescent zonally symmetric tide. Other data i
ndicate propagating tides, migrating tides, or a mixture of both.