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Abstract:
In this study we performed a detailed analysis of the ionospheric currents at different latitudes derived from the single- and dual-spacecraft (dual-SC) approaches of ESA’s Swarm constellation. We found at low and middle latitudes, the inter-hemispheric field-aligned current (IHFAC) derived from both approaches agree qualitatively with each other for all seasons, but the amplitudes of single-spacecraft results reach only about 70% of those from the dual-SC. This difference between IHFACs is attributed to the fact that only the magnetic field By component is utilized in the single-satellite approach, while both Bx and By components are considered in the dual-SC approach. Above the magnetic equator, the ionospheric radial current from single-spacecraft approach shows spurious tidal signatures, caused by equatorial electrojet (EEJ) contributions to the component, while the EEJ does not contaminate dual-satellite results. At auroral latitudes, similar underestimation of FACs from the single-spacecraft is also found at both dawn and dusk sides, with most prominent deviations at latitudes between the Region 1 and Region 2 currents. Our results confirm that the advanced current estimates from the Swarm dual-SC approach provide a good opportunity for better understanding the ionospheric current system.
