In a recent study of IMAGE FUV data, Frey et al. <2003> examined cases of high-latitude dayside aurora (HiLDA) caused by precipitating electrons predominantly during northward IMF with a strongly positive IMF By component. To determine the conditions that control these auroral emissions, we examine field-aligned currents observed by the Iridium constellation for 25 events of prolonged steady IMF orientation with both Bz and By positive. We find that localized FACs are sustained under all observed solar wind conditions, but that the occurrence of HiLDA is generally restricted to solar wind proton densities below 4 cm-3 and peak current densities higher than 0.7 ¿A/m2. That the solar wind density orders the occurrence of the auroral emissions indicates that magnetosheath plasma has ready access to the field lines carrying the upward current. Assuming that the magnetosheath plasma density and temperature govern the high-altitude conditions on these field lines, we find that the intensity of the HiLDA emissions correlates with an estimate for the particle precipitation energy density based on the Knight relation, using the measured current density and the magnetosheath temperature and density.