The Birkland Currents, the Electrojets, Auroral Precipitation, Intense Electric Field Channels, and the Open-Closed Field Line Boundary: A Synthesis of Quiet Time Auroral Current Structure Near the Harang Discontinuity.

Abstract:

The European Space Agency Swarm satellite mission began with all three Swarm satellites in similar, noon-to-midnight polar orbits. We present electric field, magnetic field, electron density, electron temperature, and ion temperature measurements from early in the Swarm mission (December 2013). This data set is of particular interest as the pearls-on-a-string orientation of the satellites provide multiple measurements of similar volumes of space taken minutes apart, providing confidence in measurement integrity and reducing the spatio-temporal ambiguity inherent to in-situ measurements. Furthermore, the measurement period is characterized by low geomagnetic activity which results in consistent measurement conditions orbit to orbit.

The December 2013 ionospheric Swarm measurements combined with ground-based optical and magnetic measurements provide a consistent picture of ionospheric and field-aligned currents near midnight during quiet geomagnetic conditions. Relationships between large-scale field aligned currents, auroral precipitation, narrow regions of enhanced electric fields, the electrojets, and the open-closed field line boundary have all been studied pairwise previously. We present a synthesis interpretation of the set of measurements to arrive at a consistent picture of the auroral current structure near midnight.

This work is supported by a grant from the Canadian Space Agency.