4:30 PM - 4:45 PM
[PEM11-23] Seasonal Dependence of the Quasi-6-Day Oscillation in the Sq-EEJ current system
Keywords:the Quasi-6-Day Wave, the Quasi-6-Day Oscillation, Sq-EEJ current system, Principal component analysis, GAIA model, Seasonal dependence
Day-to-day variations in the Sq-EEJ current system using dense geomagnetic field observational sites along 210°geomagnetic longitude chain composed of MAGDAS (Global Geomagnetic Observation Network) and observational sites operated by Geospatial Information Authority of Japan (GSI) and INTERMAGNET were analyzed for a comprehensive understanding of coupling processes in the atmosphere-ionosphere system. In this study, we focus on the quasi-6-day oscillation excited by atmospheric waves from lower atmosphere.
The quasi-6-day wave (Q6DW), one of the atmospheric waves, is excited in the lower atmosphere and propagates into thermosphere. Using CHAMP, Swarm and Aura satellites, Yamazaki et al. showed that the quasi-6-dayoscillation in the EEJ occurs when the Q6DW in the mesosphere is enhanced. This suggests that the quasi-6-day oscillation in the EEJ is caused by the Q6DW propagated from below. However, the seasonal dependences and global characteristics of the quasi-6-day oscillation in the Sq-EEJ current system are not well known.
To understand the global distribution of the quasi-6-day oscillation in the Sq-EEJ current system, we analyzed magnetic field data of MAGDAS, GSI, and INTERMAGNET during 2007-2011. We used Principal component analysis to eliminate disturbance components and to extract the magnetic field variation caused by the Sq-EEJ current system more clearly. In this case, we used the first to fifth order components added together as the basic components. In addition, to ensure that the quasi-6-day oscillations are not affected by the amplitude of the background magnetic field, we expressed them in terms of relative amplitudes as used in [Yamazaki et al. 2018].
Our results indicate that the quasi-6-day oscillation in the Sq-EEJ current system more strongly developed in the mid-latitude Sq current system than in the EEJ, and more strongly developed in the day side. The quasi-6-day oscillation in the magnetic field data of the GAIA model and MAGDAS have similar seasonal variation and global characteristics. This result indicates the usefulness of the relative amplitude. The quasi-6-day oscillation is strongly developed in equinoxes, which is consistent with the seasonal dependence of the excitation source, the Q6DW.
In the future, we will analyze how the Q6DW effects on the electrical conductivity and generates the electric field with the GAIA model. That leads to understand coupling processes in the atmosphere-ionosphere system.
The quasi-6-day wave (Q6DW), one of the atmospheric waves, is excited in the lower atmosphere and propagates into thermosphere. Using CHAMP, Swarm and Aura satellites, Yamazaki et al. showed that the quasi-6-dayoscillation in the EEJ occurs when the Q6DW in the mesosphere is enhanced. This suggests that the quasi-6-day oscillation in the EEJ is caused by the Q6DW propagated from below. However, the seasonal dependences and global characteristics of the quasi-6-day oscillation in the Sq-EEJ current system are not well known.
To understand the global distribution of the quasi-6-day oscillation in the Sq-EEJ current system, we analyzed magnetic field data of MAGDAS, GSI, and INTERMAGNET during 2007-2011. We used Principal component analysis to eliminate disturbance components and to extract the magnetic field variation caused by the Sq-EEJ current system more clearly. In this case, we used the first to fifth order components added together as the basic components. In addition, to ensure that the quasi-6-day oscillations are not affected by the amplitude of the background magnetic field, we expressed them in terms of relative amplitudes as used in [Yamazaki et al. 2018].
Our results indicate that the quasi-6-day oscillation in the Sq-EEJ current system more strongly developed in the mid-latitude Sq current system than in the EEJ, and more strongly developed in the day side. The quasi-6-day oscillation in the magnetic field data of the GAIA model and MAGDAS have similar seasonal variation and global characteristics. This result indicates the usefulness of the relative amplitude. The quasi-6-day oscillation is strongly developed in equinoxes, which is consistent with the seasonal dependence of the excitation source, the Q6DW.
In the future, we will analyze how the Q6DW effects on the electrical conductivity and generates the electric field with the GAIA model. That leads to understand coupling processes in the atmosphere-ionosphere system.