Seasonal and local time dependences of the interhemispheric field‐aligned currents deduced from the Ørsted satellite and the ground geomagnetic observations

Abstract

The precise magnetic field measurements by the Ørsted satellite revealed a distinct spatial variation of the eastward component residual (ΔBϕ) at mid and low latitudes on the dayside. This magnetic field variation was attributed to the interhemispheric field‐aligned currents (IHFACs) at mid and low latitudes based on its comparison with ground geomagnetic field variations. These IHFACs were found to flow from the summer hemisphere to the winter hemisphere in the dawn sector, and from the winter hemisphere to the summer hemisphere in the noon and the dusk sectors. These IHFACs flip their direction not at equinoxes but in May and November. The current intensity of the IHFACs is largest not at solstices but in February and August. The ground‐based geomagnetic field observations at 17 low latitude stations also support the seasonal dependence and local time distribution of the IHFACs.