In the ''classical'' theory of the polar wind, there is a significant outflow of cold supersonic H+ and limited O+ from the polar ionosphere. Recent DE 1 observations in the polar cap region report upflowing field-aligned H+ and O+ beams (~10 eV) which may interact with the polar wind. The source of these ion beams may be energetic ions in the dayside polar cusp that E¿B convect into the polar cap region. These ion beams provide free energy to the polar wind which will alter its ''classical'' decription. In the study described here, the linear as well as the nonlinear effects of O+ and H+ ion beams on an O+ and H+ polar wind are investigated. The O+ and H+ polar wind ions are modeled by isotropic Maxwellian distributions while the electrons, O+ beam ions, and H+ beam ions are modeled by drifting Maxwellian distributions. The electrostatic dispersion relation is solved for a range of O+/H+ beam densities, Te/Ti, and ion beam speeds. There is a parameter regime consistent with observations in which O+ beam modes such as the slow O+ acoustic and slow O+ cyclotron modes are excited with growth rates &ggr;~&OHgr;O while H+ beam modes are damped. Simulations show that these O+ beam modes heat both the O+ and H+ polar wind ions in the perpendicular direction. In fact, the O+ ions are preferentially heated over the H+ ions. This preferential heating of O+ ions has important implications because it enhances the outflow of O+ ions along polar capfield lines by effectively increasing the O+ scale height. ¿American Geophysical Union 1990