Swarm Observations of Field-Aligned Currents Associated with Pulsating Auroras and Multiple Auroral Arcs

Abstract:

The European Space Agency's three Swarm satellites, in orbit since late 2013, provide precise, multi-point measurements of electric and magnetic fields from circular polar orbits. When used in conjunction with ground-based camera arrays including the THEMIS white-light cameras, the number of satellite-ground conjunctions is large and growing, and is providing an unprecedented number of opportunities to explore the detailed relation between field-aligned currents and auroral forms. In this study we focus on two specific morphologies, namely pulsating auroras and multiple, parallel auroral arcs. We find that pulsating auroras are essentially always accompanied by FAC fluctuations having amplitudes comparable to those found within discrete arcs: several μA/m². The ubiquity and intensity of these currents raise the question of the degree to which electrodynamic coupling to the ionosphere affects the formation and evolution of pulsating patches. In the case of multiple, parallel discrete arcs, we ask the question of whether multiple arc systems respresent a collection of multiple up/down current pairs, or whether instead each arc is an intensification within a broad, unipolar current sheet.

This research is supported by the Canadian Space Agency and the European Space Agency