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[PEM13-P04] Spectral analysis of the phase velocity distribution of AGWs and MSTIDs in airglow images at Darwin – Preliminary comparison with airglow images at Sata, Japan
Keywords:Atomospheric Gravity Waves (AGWs), Medium-Scale Traveling Ionospheric Disturbances (MSTIDs), Airglow images, Statistical analysis
Atmospheric gravity waves (AGWs) and medium-scale traveling ionospheric disturbances (MSTIDs) in the upper atmosphere affect the atmospheric circulation and the radio-wave transmission including satellite positioning, respectively. These waves can be observed in nocturnal airglow images. Thus, spectral analysis of airglow images provides propagation direction and power of these waves. However, such spectral analysis of airglow images has not been done yet for stations in the southern hemisphere except for Antarctica. In this study, we calculated the horizontal phase velocity distribution of AGWs and MSTIDs by applying the 3-dimensional spectral analysis method of Matsuda et al. [JGR, 2014] to the airglow images obtained at Darwin (12.4°S, 131.0°E) in Australia from 2001 to 2007 and from 2011 to 2019.
Horizontal phase velocity spectra of AGWs in the mesopause region are obtained from airglow images at a wavelength of 557.7 nm. The spectra show clear characteristics that the northwestward power spectral density is weaker in summer and during the La Niña periods. We also found that tropospheric convection was missing at southeast of Darwin during these periods. These results suggest that the tropospheric convection is a possible source of AGWs in the mesopause region.
Horizontal phase velocity spectra of MSTIDs are obtained from airglow images at a wavelength of 630.0 nm. The spectra show that the northwestward power spectral density is stronger in winter and during solar quiet periods. These features can be explained if the observed MSTIDs are caused by the ionospheric Perkins instability. We speculate that the MSTIDs propagating other directions may be generated by AGWs.
In the present study, we also analyzed airglow images obtained at Sata (31.0°N, 130.7°E), Japan, from 2000 to 2020. Darwin and Sata are located nearly at geomagnetic conjugate points, but geographically Darwin is located at lower latitudes (12.4°S) than Sata (31.0°N), The climate and surrounding topographic conditions are very different between Darin and Sata. In this presentation, we discuss the similarity and difference of airglow spectra between Darwin and Sata, considering the difference of the geographic and magnetic characteristics.
Acknowledgement
The operation of the all-sky imager at Darwin has been carried out with support of the Space Weather Services (SWS) of the Bureau of Meteorology, Australia.
Horizontal phase velocity spectra of AGWs in the mesopause region are obtained from airglow images at a wavelength of 557.7 nm. The spectra show clear characteristics that the northwestward power spectral density is weaker in summer and during the La Niña periods. We also found that tropospheric convection was missing at southeast of Darwin during these periods. These results suggest that the tropospheric convection is a possible source of AGWs in the mesopause region.
Horizontal phase velocity spectra of MSTIDs are obtained from airglow images at a wavelength of 630.0 nm. The spectra show that the northwestward power spectral density is stronger in winter and during solar quiet periods. These features can be explained if the observed MSTIDs are caused by the ionospheric Perkins instability. We speculate that the MSTIDs propagating other directions may be generated by AGWs.
In the present study, we also analyzed airglow images obtained at Sata (31.0°N, 130.7°E), Japan, from 2000 to 2020. Darwin and Sata are located nearly at geomagnetic conjugate points, but geographically Darwin is located at lower latitudes (12.4°S) than Sata (31.0°N), The climate and surrounding topographic conditions are very different between Darin and Sata. In this presentation, we discuss the similarity and difference of airglow spectra between Darwin and Sata, considering the difference of the geographic and magnetic characteristics.
Acknowledgement
The operation of the all-sky imager at Darwin has been carried out with support of the Space Weather Services (SWS) of the Bureau of Meteorology, Australia.