Observations of ionospheric and field-aligned currents in the late afternoon sector with TRIAD and the Scandinavian Magnetometer Array

A three-dimensional model current system is fitted to simultaneous Scandinavian Magnetometer Array and TRIAD observations of magnetic disturbances in the dusk sector. It was possible to determine quantitatively the parameters of the main current loops and to get relevant information on the coupling between ionospheric and field-aligned currents in the dusk and also partially in the dawn sector. Evidence is presented that the model current system is at least qualitatively representative of the magnetic observations obtained by ISIS-2, TRIAD and the Alberta magnetometer chain, and that it can resolve an apparent contradiction that resulted from ambiguities when interpreting either groundbased or satellite magnetic measurements alone. Calculation of the Hall-to-Pedersen conductivity ratio along the TRIAD trajectory from magnetic measurements alone enabled conclusions to be drawn about the energy of precipitating particles along that meridian.