Electrodynamic Parameters of the Auroral Oval from Combined Spacecraft and Ground Measurements
Spacecraft traversing the auroral oval respond primarily to the field-aligned currents at its poleward and equatorward borders that are part of a solenoidal current system. If electric and magnetic field measurements are done, it is possible to determine the integrated Pedersen conductivity of the auroral oval. On the ground, however, one detects primarily the magnetic effects of the Hall currents associated with the auroral oval electric field. If the Hall current can be determined, along with the electric field, one can obtain the Hall conductivity. Inversion of magnetic perturbations in the meridian traversed by the spacecraft can give the Hall current. The Automated Forward Modelling (AFM) method permits this to be done effectively. The method is described with an example based on FAST over the Churchill meridian in Canada. Studying temporal and spatial variations needs multiple instrumented meridians and spacecraft. Efforts to increase the number of instrumented meridians in Canada are described.