Three-dimensional Fourier analysis of atmospheric gravity waves and medium-scale traveling ionospheric disturbances observed in airglow images in Hawaii over three years

Abstract:

We studied atmospheric gravity waves (AGWs) in the mesopause region and medium-scale traveling ionospheric disturbances (MSTIDs) in the thermosphere using a three‐dimensional spectral analysis technique for airglow images obtained at wavelengths of 557.7 nm (altitude: 90–100 km for AGWs) and 630.0 nm (200–300 km for MSTIDs) during the three years from 2013 to 2016 at Haleakala (21^oN, 156^oW) in Hawaii. The latitude, longitude, and orography of Hawaii are greatly different from the observation points where this spectral analysis technique has been applied to airglow images. The three-year averages of the phase velocity spectra of AGWs observed in airglow images at a wavelength of 557.7 nm show no difference in the zonal propagation between summer and winter. The power spectral density (PSD) tends to be larger in northward in summer and southward in winter. The correspondence rate by propagation direction between the upward flow in the troposphere and AGWs was ~70%. The PSDs of MSTIDs were strongest in winter and the waves propagate mainly in the east-west direction. We consider the possibility of generating these MSTIDs by AGWs in the thermosphere. The correspondence rate between the upward flow in the troposphere and MSTIDs was ~68%. We will also report the correspondence between the upward flow in the troposphere and the PSDs of AGWs or MSTIDs and the relation between the PSDs of mesospheric AGWs and MSTIDs.