Latitudinal and interhemispheric differences of the ionospheric semi-diurnal lunitidal perturbations during the 2009 Arctic sudden stratospheric warming event in the eastern Asia\u2013Australia sector

Abstract

The ionosphere exhibits some characteristic perturbations during sudden stratospheric warming (SSW) events, of which the mechanism is not thoroughly understood. This study focuses on the latitudinal and interhemispheric differences of the enhanced semi-diurnal lunitidal (M2) perturbations related to SSW using total electron content calculated from the network of Global Navigation Satellite System and ionosonde data in the eastern Asia–Australia sector during the January 2009 SSW. Our results show that the most distinct M2 perturbations in the northern and southern hemispheres occur near the Equatorial Ionization Anomaly crest regions around ± 15° geomagnetic latitudes, but corresponds to different moon phases, respectively. Clear M2 perturbations extend to middle latitudes only in the southern hemisphere and have another local maximum in the southern middle latitude. Such latitudinal and interhemispheric features of ionospheric M2 perturbations in the low latitude in the eastern Asia–Australia sector are similar as those in the American sector during the same SSW event. This supports previous suggestion that such latitudinal and interhemispheric differences in the low latitude can be primarily explained by the summer–winter thermospheric wind modulation on equatorial plasma fountain and thus emphasize its role in the vertical coupling process of M2 perturbation. The clear differences of M2 perturbations in the southern middle latitude between the eastern Asia–Australia and American sectors indicate that the thermospheric circulation related to the Weddell Sea Anomaly may have influence on the lower atmosphere–ionosphere coupling.Graphical