The phases and amplitudes of gravity waves propagating and dissipating in the thermosphere: Application to measurements over Alaska

In a companion paper, we derived the high-frequency, compressible, dissipative polarization relations for gravity waves (GWs) propagating in the thermosphere. In this paper, we apply the results to nighttime thermospheric observations of a GW over Alaska on 9-10 January 2010. Using a vertically-pointed Fabry-Perot interferometer (FPI) at Poker Flat that measured vertical wind perturbations (w') and two FPIs that measured the line-of-sight (LOS) velocities in four common volumes, we inferred a GW ground-based period similar to 32.7 +/- 0.3 min, horizontal wavelength lambda(H) = 1094 +/- 408 km, horizontal ground-based phase speed c(H) similar to 560 +/- 210 m/s, and propagation azimuth theta similar to 33.5 +/- 15.8 degrees east-of-north. We compared the phase shifts and amplitude ratios of this GW with that predicted by the GW dissipative polarization relations derived in the companion paper, enabled by the ability of the FPIs to measure fundamental GW parameters (wind and temperature perturbations). We find that GWs with lambda(H) similar to 700-1100 km, lambda(z) similar to -500 to -350 km, theta similar to 15 to 50 degrees, and c(H) similar to 350-560 m/s agree with the observations if the primary contribution to the 630-nm emission was near the upper portion of that layer. The source of GW was likely thermospheric given the large intrinsic phase speed of the wave. Possible sources are discussed, the most likely of which are related to the onset of auroral activity near the time that the wave was initially observed.