Unique morphology of Interhemispheric Field-aligned Currents and the Associated Factors and Mechanism

The classic ionospheric dynamo theory suggests the Interhemispheric Field-Aligned Currents (IHFACs) are season and local time dependent that arises from asymmetric ionospheric conductivities and thermospheric winds between the northern and southern hemispheres. Recent studies showed IHFACs have extremely longitudinal variations and show “C”-shaped morphology in Atlantic-American region that beyond previous thought. However, there are less detailed studies about the mechanism for the reversal phenomenon. This study analyzed Pedersen conductivity in the two hemispheres and geomagnetic structure to investigate the reasons for the reversal of IHFACs. The result suggests the geomagnetic declination connects the ionosphere in the two hemispheres at different local times, causing large conductance asymmetry. The conductance asymmetry exceeding 10 S will result in the reversal of IHFACs. This study further discussed the mechanism of the reversal and the impact on the ionosphere to reveal the regional electrodynamic process.