17:15 〜 19:15
[PEM12-P22] The meridional currents of the equatorial electrojet as seen from ground magnetic data through principal component analysis
キーワード：equatorial electrojet, prinicpal component analysis, meridional currents, ground magnetic data
The equatorial electrojet (EEJ) is a prominent eastward geomagnetic current flowing at the magnetic dip equator, primarily recognized through its significant influence on the H (northward) magnetic component as observed from the ground. Besides its main eastward flow, the EEJ encompasses meridional currents flowing perpendicular to the main current, whose effect, if any, on the main eastward current is less understood.
This study hypothesizes that the intensification and decay of the EEJ is at least partially due to the diverging and converging nature of the meridional currents. Ground magnetic data, specifically the D (eastward) magnetic component, was analyzed through principal component analysis (PCA), focusing on obtaining the spatiotemporal variations of the meridional current signal and on isolating this effect from other concurrent geomagnetic influences, such as the inter-hemispheric field-aligned currents (IHFACs).
Data from several ground magnetic stations near the dip equator in Southeast Asia (SEA) and South America (SA) was analyzed through PCA. For SEA, the meridional current signal was identified as the second principal component. This component was also linked to the intensification of the EEJ, as well as the global Sq currents. This identification was further supported by the longitudinal variation of the observed signal. For SA, however, a possible asymmetry of the meridional currents between the hemispheres was identified, possibly arising from the asymmetry in the Sq currents over SA.
These findings demonstrate the potential of PCA in distinguishing EEJ-related magnetic signatures from other geomagnetic phenomena found in ground-based observation data, offering insights into the three-dimensional structure of the EEJ. Future efforts will aim at validating these results through methodological refinement and comparative analyses with models, satellite data, and other resources.
This study hypothesizes that the intensification and decay of the EEJ is at least partially due to the diverging and converging nature of the meridional currents. Ground magnetic data, specifically the D (eastward) magnetic component, was analyzed through principal component analysis (PCA), focusing on obtaining the spatiotemporal variations of the meridional current signal and on isolating this effect from other concurrent geomagnetic influences, such as the inter-hemispheric field-aligned currents (IHFACs).
Data from several ground magnetic stations near the dip equator in Southeast Asia (SEA) and South America (SA) was analyzed through PCA. For SEA, the meridional current signal was identified as the second principal component. This component was also linked to the intensification of the EEJ, as well as the global Sq currents. This identification was further supported by the longitudinal variation of the observed signal. For SA, however, a possible asymmetry of the meridional currents between the hemispheres was identified, possibly arising from the asymmetry in the Sq currents over SA.
These findings demonstrate the potential of PCA in distinguishing EEJ-related magnetic signatures from other geomagnetic phenomena found in ground-based observation data, offering insights into the three-dimensional structure of the EEJ. Future efforts will aim at validating these results through methodological refinement and comparative analyses with models, satellite data, and other resources.