Particle-in-cell simulations of solitary waves have been performed using a 2 spatial and 3 velocity dimension electrostatic code with one electron and two ion species. Data from the Fast Auroral Snapshot (FAST) and Polar spacecraft are used to provide input parameters, and on the basis of these observations, no cold plasma was included in contrast to earlier simulations. Simulations containing both oxygen and hydrogen beams are compared to simulations that contain only hydrogen to examine the effects of the oxygen on the behavior of the solitary waves. In both cases the solitary wave speeds are less than the hydrogen beam speed, and they are also greater than the oxygen beam speed for the cases including oxygen. The simulated solitary waves have spatial scales of the order of 10 &lgr;D and potential amplitudes of the order of 0.1 eϕ/kTe, which are consistent with Polar spacecraft observations in the low-altitude auroral zone. ¿ 2001 American Geophysical Union