The high-latitude ionosphere is not homogeneous, especially for winter conditions. In the winter dayside high-latitude ionosphere the terminator often appears equatorward of the cusp region where sources of geomagnetic disturbances are thought to be located. In these cases, when the cusp region appears in darkness, secondary field-aligned currents arise on the terminator because of the redistribution of ionospheric currents in the conjugate summer sunlit ionosphere where the conductivity is significantly higher. This work presents results of calculations using a numeric model that was elaborated for the study of the potential and 3D currents in two hemispheres with different ionospheric conductivities. The interhemispheric field-aligned currents are shown to arise near the terminator position, leading to the formation of vortices in equivalent ionospheric currents, which can be detached from sources of the electric potential and lie several degrees equatorward of the potential sources. ¿ 2000 American Geophysical Union