The distribution of equivalent current vectors of polar magnetic substoms, relative to luminous auroral features of global scale, is examined by comparing a number of DMSP satellite photographs with the simultaneous ground magnetic data. The westward aurotal electrojet is the domainant feature. It flows along the diffuse aurora in the midnight and morning sectors as well as along the vicinity of active westward traveling surges in the evening sector. The present study confirms the early finding by Harang (1946) and Akasofu et al. (1965) that the westward electrojet does not end in the midnight meridian but that it extends into the evening sector along the poleward half of the auroral oval. The eastward current flows mostly equatorward of discrete auroras (perhaps along the diffuse aurora) in the evening sector, but sometimes it flows near or in the region of discrete arcs of a stretched or looped form. An accurate distribution of the westward and eastward currents across an evening meridian cannot, however, be obtained from the present study. |