5:15 PM - 6:45 PM
[PEM12-P32] Elucidating the three-dimensional Sq-EEJ current system: The role of polarization effects utilizing the GAIA electrodynamics component
Keywords:ionospheric simulation, potential solver, Atmosphere-Ionosphere coupling, Sq-EEJ current system
During quiet geomagnetic conditions, the Sq-EEJ current system is well recognized. However, the differentiation between Pedersen and Hall currents within the vortex and the reasons behind their specific structures remain unclear.
Previous research has attempted to address these questions, yet most explanations of Sq current omit the presence of Hall current [e.g., Ryu et al., 2022]. Fukushima [1968; 1979] divided the current system into two parts using the concept of polarization, but this theory was incomplete, failing to account for current closure and field-aligned currents in the ionosphere. Later, Takeda [1991] analyzed the current system both with and without Hall conductivity, highlighting the significance of the Cowling effect in the formation of Sq current without establishing a theoretical causality.
Recent theories on current formation through polarization under the quasi-electrostatic assumption by Yoshikawa et al. [2013], along with theoretical predictions on the three-dimensional causality of Sq current formation [Yoshikawa et al., AGU Fall Meeting 2012], necessitate verification through numerical and theoretical simulations.
Utilizing the electrodynamics component of GAIA (Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy) [Jin et al., 2011], with a tilted dipole field and divergent neutral wind, we discovered that the primary sources of Sq-EEJ system formation are the polarization effects due to the divergence of the wind dynamo field and the conductivity gradient at dawn and dusk. Although the impact is minor, the north-south gradient in conductivity alters the focal points of Sq vortices. Furthermore, we confirmed the presence of a meridional loop current as predicted in previous studies [Fukushima, 1968; Yoshikawa et al., AGU Fall Meeting 2012]. Contrary to prior assumptions that Sq current flows on a horizontal plane, our findings indicate that it also has vertical components.
Previous research has attempted to address these questions, yet most explanations of Sq current omit the presence of Hall current [e.g., Ryu et al., 2022]. Fukushima [1968; 1979] divided the current system into two parts using the concept of polarization, but this theory was incomplete, failing to account for current closure and field-aligned currents in the ionosphere. Later, Takeda [1991] analyzed the current system both with and without Hall conductivity, highlighting the significance of the Cowling effect in the formation of Sq current without establishing a theoretical causality.
Recent theories on current formation through polarization under the quasi-electrostatic assumption by Yoshikawa et al. [2013], along with theoretical predictions on the three-dimensional causality of Sq current formation [Yoshikawa et al., AGU Fall Meeting 2012], necessitate verification through numerical and theoretical simulations.
Utilizing the electrodynamics component of GAIA (Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy) [Jin et al., 2011], with a tilted dipole field and divergent neutral wind, we discovered that the primary sources of Sq-EEJ system formation are the polarization effects due to the divergence of the wind dynamo field and the conductivity gradient at dawn and dusk. Although the impact is minor, the north-south gradient in conductivity alters the focal points of Sq vortices. Furthermore, we confirmed the presence of a meridional loop current as predicted in previous studies [Fukushima, 1968; Yoshikawa et al., AGU Fall Meeting 2012]. Contrary to prior assumptions that Sq current flows on a horizontal plane, our findings indicate that it also has vertical components.