Coincident two-station optical auroral data and magnetic field measurements from the polar-orbiting satellite Magsat have allowed the comparison of the positions of small-scale disturbances in the magnetic field with the positions of optical forms over Spitsbergen. For one discrete arc seen at 0715 UT on January 15, 1980, we have found at the position of intercept between the satellite and arc a narrow sheet of enhanced current density embedded in a broader region of lower current density which appears to mark the poleward boundary of the upward current region (region 2). Other simultaneous optical and magnetic field measurements made at 1500 UT on January 19, 1980, indicate that multiple arcs were embedded in the broad region of upflowing current with a bright arc close to the boundary between the auroral oval and polar cap. |