5:15 PM - 6:45 PM
[PEM12-P26] Seasonal Variation and Latitudinal Structure of the Quasi-6-Day Wave on the Inter-Hemispheric Field-Aligned Currents (IHFACs)
Keywords:Quasi-6-Day Wave, Principal Component Analysis, Inter-Hemispheric Field-Aligned Currents , Atmospheric Tides
The quasi-6-day wave (Q6DW) is a type of atmospheric wave generated by the latent heat heating associated with the cumulus convection activity in the tropics [Miyoshi and Hirooka, 1999]. It propagates upward and affects the equatorial electrojet (EEJ) in the ionosphere, which has been confirmed from satellite observations [Yamazaki et al., 2018]. In addition, TIME-GCM calculations shows that the Q6DW reaches its maximum intensity around the equinoxes [Liu et al., 2014]. Inter-hemispheric field-aligned currents (IHFACs) flow from the ionosphere of one hemisphere to the other through the magnetosphere, to resolve the non-uniformity of ionospheric currents with divergent spatial structure that occurs between hemispheres [Fukushima, 1979]. The direction of the IHFACs changes in the morning, noon, and evening, and its intensity is highest in February and August [S. Yamashita and T. Iyemori, 2002].
In this study, we used ground magnetic field data from MAGDAS and INTERMAGNET to clarify the effects of the Q6DW on the IHFACs. The ground magnetic field data used are the east-west (D) magnetic field components at 9 stations within the 210 geomagnetic longitude band and -35 to +35 geomagnetic latitude during the 2007-2011 magnetic quiet period. Principal component analysis is a statistical analysis method that can extract large components from any data and reveal its internal structure. We applied this method to the data to extract the Sq current system and the IHFACs variations from the D component in the magnetic equator and the mid-low latitude region. The amplitude of the oscillation with a period of about 6 days (Q6DO) was extracted, and this was excited by the Q6DW. To show the latitudinal and seasonal structure of the Q6DO, the average amplitude for a given month over the 5-year timespan were calculated.
The results show that, the IHFACs are affected by the Q6DW. Also, the variation become stronger around the equinoxes, which is consistent with the seasonal dependence of the Q6DW. The latitudinal structure of the Q6DO appearing in the IHFACs has amplitudes from the equator to mid-latitudes, suggesting that the Q6DW may have been propagated between hemispheres via the IHFACs. More results and discussion will be presented in this presentation.
In this study, we used ground magnetic field data from MAGDAS and INTERMAGNET to clarify the effects of the Q6DW on the IHFACs. The ground magnetic field data used are the east-west (D) magnetic field components at 9 stations within the 210 geomagnetic longitude band and -35 to +35 geomagnetic latitude during the 2007-2011 magnetic quiet period. Principal component analysis is a statistical analysis method that can extract large components from any data and reveal its internal structure. We applied this method to the data to extract the Sq current system and the IHFACs variations from the D component in the magnetic equator and the mid-low latitude region. The amplitude of the oscillation with a period of about 6 days (Q6DO) was extracted, and this was excited by the Q6DW. To show the latitudinal and seasonal structure of the Q6DO, the average amplitude for a given month over the 5-year timespan were calculated.
The results show that, the IHFACs are affected by the Q6DW. Also, the variation become stronger around the equinoxes, which is consistent with the seasonal dependence of the Q6DW. The latitudinal structure of the Q6DO appearing in the IHFACs has amplitudes from the equator to mid-latitudes, suggesting that the Q6DW may have been propagated between hemispheres via the IHFACs. More results and discussion will be presented in this presentation.