Using linear inversion techniques developed by Oldenburg (1976, 1977), the auroral electrojet configuration in the evening sector is studied with a view to finding the local time dependence of the westward electrojet which flows at the poleward edge of the eastward electrojet. Specific current systems whose magnetic field perturbations fit the observations to within a specified rms error are developed which, in conjunction with the inversions, yield useful information on the current density across the electrojets. It is found that the westward electrojet penetrates up to the dusk meridian for periods of moderate activity even though substorms are not necessarily in progress.