Using two-dimensional observations from the spinning, polar-orbiting S3-3 satellite, we have compared the locations of regions that we identify as discrete auroral arcs with regions of isotropic ion precipitation. Regions of discrete auroral arcs are defined to be regions containing particle distributions consistent with field-aligned potential drops >0.5 kV. Polar cap arcs and local times near noon (0900--1500 MLT) are excluded from this study. Our most important result is that the inferred locations of discrete auroral arcs are almost exclusively confined to the region of isotropic ion precipitation at all local times studied. In the rare exceptions, the ion pitch angle distributions approach isotropy. This association is what is expected if magnetic field lines containing discrete auroal arcs thread the tail current sheet at distances where ion motion violates the guiding center approximations. We have also found that discrete arc regions are generally associated with spatial structure and boundaries in the precipitating ions. Additionally, we occasionally observe upward going, return-current electrons, and these are also associated with the structured, isotropic ion precipitation. ¿ American Geophysical Union 1988