We compare auroral images from the Polar ultraviolet imager (UVI) and simultaneous particle observations from the Defense Meteorological Satellite Program (DMSP) in the afternoon (1300--1600 MLT) sector along the oval in the northern hemisphere to determine the magnetospheric source region of postnoon auroral bright spots. Auroral bright spots are determined with Polar UVI, while their magnetospheric source regions are determined from DMSP F13 particle data. A total of 65 events of good temporal and spatial coincidence were identified after searching through over 1 year of data, from April 1996 to June 1997. Instances occur of auroral arcs mapping to each of several different regions, including the plasma sheet, the low-latitude boundary layer, and the plasma mantle. However, our results indicate that ~2/3 of the time the most prominent auroral arcs are associated with plasma sheet electron precipitation and slightly less than 1/3 of the time they are found to occur near (less than 1¿ in magnetic latitudes) the boundary between the plasma sheet and other regions. ¿ 1999 American Geophysical Union