[P-EM14] Study of coupling processes in solar-terrestrial system

[PEM14-P05] Estimation of Horizontal Wind Speed from Gravity Wave Structures in Airglow Images

*Shin Suzuki¹, Kazuo Shiokawa² (1.Faculty of Regional Policy, Aichi University, 2.Institute for Space-Earth Environmental Research, Nagoya University)

Keywords:airglow, gravity waves

In this study, we estimate wind speed near the mesopause by observing atmospheric gravity waves using airglow imaging. According to the linear dispersion relation for gravity waves, the vertical wavelength can be derived from the intrinsic velocity (the difference between the horizontal phase velocity and the background wind) and the horizontal wavelength. In airglow imaging, both the horizontal phase velocity and horizontal wavelength of the waves can be directly obtained from the images. Assuming that the same wave structure is observed in airglow emissions at different altitudes, the horizontal-to-vertical wavelength ratio can be calculated from the phase difference between the wavefronts observed in two airglow images and the altitude difference of the airglow layers. This approach enables the determination of the background wind speed solely from airglow observations.
In this study, we present preliminary statistical results for horizontal wind speed estimates derived from seven events of small-scale gravity waves observed by the Optical Mesosphere Thermosphere Imager (OMTI) at Shigaraki Station, Japan (136.1°E, 34.8°N). These events exhibited clear wave structures in both OI airglow (at 95 km) and OH airglow (at 85 km). Additionally, simultaneous observations of horizontal wind speed at the OI airglow height were made using a Fabry-Perot interferometer (FPI), allowing us to evaluate the accuracy of this estimation technique.