Videotapes of auroras from two space shuttle missions were analyzed to determine the locations of auroral rays. One hundred and forty auroral ray locations were determined by triangulating from pairs of images taken several seconds (20--100 km ) apart. The rays, observed over a range of 18 hours in local magnetic time between 62¿ and 85¿ magnetic latitude, were mostly confined to the Feldstein oval in the evening and midnight sectors but were uniformly scattered well into the polar cap in the morning sector. Plots of ray border altitude versus magnetic time show a steady increase in lower border altitude, suggesting a decrease in energy from near 10 keV in the early evening to near 2 keV by midmorning. This variation for the energy in discrete rayed arcs is opposite to previous reports for the average energy of auroral electrons and suggests that the acceleration mechanism within discrete arcs differs from that pertaining to the auroral oval in general. Comparison of upper and lower border altitudes suggests a nearly monoenergetic electron flux shortly before midnight and a more extended distribution at both earlier and later times. The apparently independent variation in maximum energy and energy spread is difficult to reconcile with models involving acceleration of auroral electrons by parallel electric fields. There was only a slight dependence of border altitudes on magnetic latitude within the auroral oval, while rays in the polar cap (northward Bz) were significantly higher. ¿ American Geophysical Union 1994