Due to its special orbit-over large segments tangential to the auroral oval and at altitudes around 1600 km-FREJA provides measurements from a sparsely sampled region. Here we will introduce initial results from the magnetic field experiment. For one event occurring about an hour after midnight we investigate the fine structure of the field-aligned currents associated with a westward electrojet. From simultaneous ground-based observations we deduce the orientation and the spatial and temporal variations of the electrojet. Space-borne magnetic field measurements provide estimates of the field-aligned current density. We deduce a lower limit of 1.75 km for the thickness of field-aligned current filaments. The comparison between electric and magnetic field recordings on FREJA suggests a poor correlation of these quantities for this event. ¿ American Geophysical Union 1994