Atmospheric Airglow Fluctuations due to a Tsunami‐driven Gravity Wave Disturbance

A spectral full‐wave model is used to study the upward propagation of a gravity wave disturbance and its effect on atmospheric nightglow emissions. Gravity waves are generated by a surface displacement that mimics a tsunami having a maximum amplitude of 0.5 m, a characteristic horizontal wavelength of 400 km, and a horizontal phase speed of 200 m/s. The gravity wave disturbance can reach F region altitudes before significant viscous dissipation occurs. The response of the OH Meinel nightglow in the mesopause region (∼87 km altitude) produces relative brightness fluctuations, which are ∼1% of the mean for overhead viewing. The wave amplitudes grow as the wave disturbance propagates upward, which causes the thermospheric nightglow emission responses to be large. For overhead viewing, the brightness fluctuations are ∼50% and 43% of the mean for the OI 6300 Å and O 1356 Å emissions, respectively. The total electron content fluctuation is ∼33% of the mean for overhead viewing. For oblique viewing, the relative brightness fluctuations are slightly smaller than those obtained for overhead viewing. In spite of this, the thermospheric nightglow brightness fluctuations are large enough that oblique viewing could provide early warning of an approaching tsunami. Thus, the monitoring of thermospheric nightglow emissions may be a useful augmentation to other observational techniques of tsunami effects in the thermosphere/ionosphere system