Latitude Dependence of Interhemispheric Field‐Aligned Currents (IHFACs) as Observed by the Swarm Constellation

Key Points Two clearly different systems of IHFACs exist at low and middle latitudes, respectively, with a boundary near ±35° in magnetic latitudes The latitudinal and longitudinal structures of IHFACs depend strongly on wave forcing from the lower atmosphere, below 30 km Midlatitude IHFACs have similar climatology in equinoxes/June solstice, while those of December solstice exhibit different behavior The daytime ionospheric E region hosts a vortex of horizontal equivalent currents driven by the wind dynamo in each hemisphere: the solar quiet current system. Differences in the dynamo actions at conjugate points in the two hemispheres drive interhemispheric currents (interhemispheric field‐aligned currents [IHFACs]). Despite the long history of investigations on this topic, only a few studies have reported a latitude dependence of the IHFACs. In this study we make use of the magnetic field observations from the European Space Agency's Swarm constellation to address the latitude dependence of IHFACs in depth. At low latitudes (35° magnetic latitude) IHFAC climatology during equinoxes is generally similar to that of June solstice while that of December solstice exhibits stand‐alone behavior.