Plasma instabilities that result when a heavy ion beam is injected into the F region ionosphere are studied by using electrostatic particle simulations. The background plasma is taken to be O+ dominated with a small concentration of H+. Particle heating is studied for various beam parameter regimes. In the beam drift velocity regime, vd/vH>1, only perpendicular H+ heating is observed at low beam densities. Parallel electron and perpendicular O+ heating are also observed when the beam density is on the order of the background O+ density. Beam thermalization and slow down are observed to be small in the high beam temperature regime but become more severe for beams with temperatures on the order of those of the background particles. ¿ American Geophysical Union 1990