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‐poin...

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Veröffentlicht in:Journal of Geophysical Research: Space Physics 2012-05, Vol.117 (A5), p.n/a
Hauptverfasser: Nicolls, M. J., Vadas, S. L., Meriwether, J. W., Conde, M. G., Hampton, D.
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Sprache:eng
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Zusammenfassung: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 ∼32.7 ± 0.3 min, horizontal wavelength λH = 1094 ± 408 km, horizontal ground‐based phase speed cH ∼ 560 ± 210 m/s, and propagation azimuth θ ∼ 33.5 ± 15.8° 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 λH ∼ 700–1100 km, λz ∼ −500 to −350 km, θ ∼ 15 to 50°, and cH ∼ 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. Key Points GW amplitudes and propagation characteristics are derived using FPI measurements Comparison to dissipative GW dispersion relation shows good agreement GW sources are likely associated with aurorally generated horizontal body forces
ISSN:0148-0227
2169-9380
2156-2202
2169-9402
DOI:10.1029/2012JA017542