SuperDARN Electrostatic Potential Function Estimation of Field-Aligned Currents

Abstract

Magnetic field-aligned currents (FACs) flow between the Earth’s ionosphere and magnetosphere. The connection afforded by FACs means that magnetospheric dynamics may be discerned in ground-based observations of the ionosphere, observations such as the ionospheric plasma velocity measurements made by the Super Dual Auroral Radar Network (SuperDARN). Signatures of FACs are present in the radar data as vorticity in the ionospheric plasma flow.

In this thesis, a new method of estimating FACs on a hemispheric scale from ground-based radar observations is presented. The method produces maps of estimated FAC density divided by height-integrated ionospheric Pedersen conductivity through direct calculation from electrostatic potential (voltage) functions that are generated from SuperDARN plasma velocity measurements. Comparisons of the maps to FAC estimates obtained from ground- and satellite-based observations using established methods show good qualitative agreement. A short case study of a geomagnetic event that occurred between the evening of 31 May 2013 and the morning of 1 June 2013 is presented to demonstrate the utility of the new potential function-based method. Future applications of the new method are suggested, such as to multi-instrument studies including SuperDARN. The new method is especially useful in that it is easily automated, easily adaptable to new SuperDARN data analysis software, and provides hemisphere-scale FAC maps with the one- or two-minute cadence of the underlying SuperDARN potential functions.