TEMPERATURE AND AIRGLOW BRIGHTNESS OSCILLATIONS IN THE POLAR MESOSPHERE AND LOWER THERMOSPHERE

Large amplitude oscillations in airglow brightness and OH rotational t emperature were observed on Dec. 31, 1993, 00 UT to Jan. 1, 1994, 18 U T over Eureka (80.0 degrees N). The airglow brightnesses of atomic oxy gen O[S-1] emission at 5577 Angstrom and sodium Na (P-2(3/2,1/2)) emis sion at 5890 and 5896 Angstrom were measured by a multi-channel, merid ian scanning photometer. The Meinel OH (3,1) band brightness and rotat ional temperature were monitored by a Michelson interferometer. The pe riod of the observed oscillations was 8.4 +/- 1 h. Supporting evidence for a non-migrating tide (zero zonal wave number) explanation of thes e oscillations are an observed period close to 8 h, a large vertical w avelength as derived from the airglow emissions, and wave persistence for five complete cycles. On the other hand, the small amplitude and n egative phase of Krassovsky's ratio are not consistent with a tidal so urce for the observed oscillations. Similar 8.5 +/- 1 h variations wer e observed on Dec. 21, 1993. The case for a non-migrating tide as a so urce for these oscillations is further weakened by a 1.5 h difference in local time when these oscillations were observed to peak during the two events (which occurred 10 days apart). Explanation of the above o bservations in terms of an inertiogravity wave is favored by the relat ively infrequent appearance of these oscillations at all altitudes mon itored, the incoherency between the two events, and the fact that temp erature variations lead OH airglow brightness variations, in qualitati ve agreement with gravity wave theory. The observed lower limit to the horizontal wavelength of the wave compares with its value predicted b y the dispersion relation of inertiogravity waves. Forced planetary wa ves, observed to peak in amplitude on Dec. 21, 1993, and Jan. 1, 1994, as well as the stratospheric warming of the middle of December and en d of December/beginning of January, were likely driven by the same tro pospheric disturbance or directly related to the source of the inertio -gravity wave observed over Eureka on Dec. 21 and Dec. 31-Jan. 1, resp ectively.