  In collision-poor plasmas from space, three distinct ion-ion instabilities
can be driven by the proton beams streaming along the background magnetic
field: left-hand resonant, non-resonant, and right-hand resonant instabilities.
These instabilities are in general investigated considering only idealized
proton beams with Maxwellian velocity distributions, and ignoring the
implications of suprathermal populations, usually reproduced by the Kappa
power-laws. Moreover, the existing theories minimize the kinetic effects of
electrons, assuming them isotropic and Maxwellian distributed. In an attempt to
overcome these limitations, in the present paper we present the results of an
extended investigation of ion-ion instabilities, which show that their
dispersion and stability properties (e.g. growth rates, wave frequencies, and
the unstable wave numbers) are highly sensitive to the influence of
suprathermal populations and anisotropic electrons. These results offer
valuable explanations for the origin of the enhanced low-frequency
fluctuations, frequently observed in space plasmas and associated with proton
beams.
