Lower Thermospheric Zonal Winds Change Interhemispheric Field‐Aligned Current Directions Over Asian‐Pacific Region

Abstract Interhemispheric Field‐Aligned Currents (IHFACs) serve as the channels connecting the ionospheric current systems over the Northern and Southern Hemispheres and maintaining the balance between them. The directions of the IHFACs represent the inflow and outflow currents from one hemisphere to the other. In this study, we investigated the mechanism for the south‐north abnormal reversals of the IHFAC directions at middle and low latitudes by analyzing the field‐aligned current density from Swarm, lower thermospheric wind from TIDI and ICON, and ionospheric conductivity derived from IRI‐2020 and Nrlmsise‐00 models. The results suggest that besides the geomagnetic geometry, the south‐north hemispheric asymmetry of ionospheric conductance controls the IHFAC reversal over the American‐Atlantic region. By contrast, over the Asian‐Pacific region, the IHFACs exhibit multiple reversals across longitudes from ∼60°E to 150°W without being controlled by conductance and geomagnetic geometry. It is surprising that variations in the thermospheric winds are particularly strong over the Asian‐Pacific region, playing a significant role in modulating the IHFAC directions. The study reveals the cause of the IHFAC directions in different seasons and regions, and promotes the understanding of the connection between the ionospheric dynamo in the two hemispheres.