WAVE AND STABILITY PROPERTIES OF MULTIION PLASMAS WITH APPLICATIONS TO WINDS AND FLOWS

In many space plasma phenomena heavy ions are present in abundances wh ich are not negligible relative to protons so that the various compone nts of the plasma are mutually coupled through the Lorentz force and t he quasi-charge neutrality constraint. Some of the novel and interesti ng effects which this coupling gives rise to are discussed here within the context of wave and stability properties of the system. In partic ular we show how differential streaming between the protons and a heav ier species (such as alpha particles in the solar wind) can give rise to low frequency compressional instabilities. The effects of Coulomb c ollisions, finite Debye length and kinetic effects are also discussed and it is emphasized that collisionless Landau damping can quench such instabilities except when the ions are sufficiently cold relative to the electrons. In connection with steady flows (e.g. solar and polar w inds) it is shown how the idea of ''critical points'' must be generali zed and interpreted within the framework of the stationary waves of th e system including differential streaming, and how these ''points'' ar e intimately connected with nonlinear mutual regulation of the ion flu xes.