The generation of ion beam modes by accelerated particle distributions in the high-latitude auroral region, associated with parallel electric fields, is considered. Various particle distribution models are used, including downward accelerated electrons, a combination of trapped and backscattered electrons, and upgoing accelerated ionospheric ions (H + and O+). A numerical study of the excited modes implies that they can be characterized as either a nonresonant ion-ion two-stream mode or a resonant acoustic mode For reasonable models of the high-latitude auroral acceleration region, the nonresonant mode has a growth rate an order of magnitude greater than the acoustic mode. Approximate analytical expressions for the maximum growth rate and the corresponding frequency of the ion-ion two-stream mode are derived. Conditions are also derived that determine when the two-stream mode evolves into an acoustic mode. The frequency range of the excited waves and the frequency at peak growth compare reasonably well with observations of broadband noise in the auroral region. The results of this study suggest that ion interactions with these waves may be a viable mechanism for the observed enhancements in the parallel temperature of accelerated auroral ions. ¿American Geophysical Union 1987