It is proposed that the National Science Foundation support a GEM study designed to test models for the source of the field-aligned currents flowing into the auroral ionosphere. Utilizing data from the magnetometer, electric field probes and particle detectors on the S3-3 satellite, the predictions of the Siscoe- Sonnerup-Lotko (SSL) model for day-side field-aligned currents will be tested. A preliminary study utilizing existing data bases is proposed for the first year. In the second and third years, software will be developed to anlyze the remainder of available auroral zones passes which will then be added to the data base. This data base will provide more statistically significant tests of SSL and other models of field-aligned current generation. Testing of models of boundary layer sources of field-aligned currents is critical to the objectives of the GEM Boundary Layer Campaign. Inputs from a study of this type will be required to develop more sophisticated and realistic models. Magnetotail sources of currents will also be examined, for example by comparing the magnitude of nightside Region 1 currents to the tail lobe magnetic field for various interplanetary magnetic field conditions. Findings will provide preliminary constraints on models of coupling and field-aligned current generation to be developed as part of the upcoming GEM Campaign on Substorms.
