Ionospheric conductances and currents of a morning sector auroral arc from Swarm‐A electric and magnetic field measurements

Abstract

AbstractWe show the first ionospheric Hall and Pedersen conductances derived from Swarm magnetic and electric field measurements during a crossing of a morning sector auroral arc. Only Swarm‐A was used, with assumptions of negligible azimuthal gradients and vanishing eastward electric field. We find upward field‐aligned current, enhanced Hall and Pedersen conductances, and relatively weak electric field coincident with the arc. Poleward of the arc, the field‐aligned current was downward, conductances lower, and the electric field enhanced. The arc was embedded in a westward electrojet, immediately equatorward of the peak current density. The equatorward portion of the electrojet could thus be considered conductance dominant and the poleward portion electric field dominant. Although the electric field measured by Swarm was intense, resulting in conductances lower than those typically reported, comparable electric fields have been observed earlier. These results demonstrate how Swarm data can significantly contribute to our understanding of the ionospheric electrodynamics.