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Zusammenfassung:
Large- to medium-scale atmospheric gravity waves (AGWs) are generated by various sources, including auroral Joule heating in the lower thermosphere and tropospheric weather systems. The aurorally excited AGWs propagate globally from high-latitude sources in the lower thermosphere both upward and downward [1,2]. Equatorward propagating traveling ionospheric disturbances (TIDs) are observed by the Super Dual Auroral Radar Network (SuperDARN), Poker Flat Incoherent Scatter Radar (PFISR), and the GNSS total electron content (TEC) mapping technique. The horizontal equivalent ionospheric currents are estimated from the ground-based magnetometer data using an inversion technique. In the lower atmosphere, the equatorward propagating AGWs with attenuated amplitudes can be amplified upon over-reflection in the troposphere. They can release conditional symmetric instability leading to slantwise convection, latent heat release and intensification of extratropical cyclones [3,4], which in turn are a source of AGWs/TIDs. Southeastward propagating TIDs that originate from cold fronts of intensifying extratropical cyclones are observed in the detrended TEC maps, and by the multipoint and multifrequency continuous Doppler sounders in Czechia [5]. Ray tracing AGWs in a model atmosphere supports the observations.
[1] Mayr H.G., et al., Space Sci. Rev. 54, 297–375, 1990. doi:10.1007/BF00177800
[2] Prikryl, P., et al., Ann. Geophys. 23, 401–417, 2005. doi.org/10.5194/angeo-23-401-2005
[3] Prikryl P., et al., Ann. Geophys. 27, 31–57, 2009. doi:10.5194/angeo-27-31-2009
[4] Prikryl P., et al., J. Atmos. Sol.-Terr. Phys. 171, 94–10, 2018. doi:10.1016/j.jastp.2017.07.023
[5] Chum J., et al., Earth Planets Space 73, 60, 2021. doi.org/10.1186/s40623-021-01379-3
