Drift eigenmodes in plasmas with negative ions

The instabilities associated with drift waves can be suppressed (or even removed) by introducing negative ions into the usual electron ion plasma. The presence of negative ions causes a decrease in the amplitude of the perturbed electrostatic fields which are mainly produced by the difference of electron and ion masses. It is shown that the presence of negative ions is a stabilizing effect for drift eigenmode in a slab geometry and the frequency of this electrostatic mode is reduced. In a pure pair-ion plasma the convective cell mode can become unstable because of shear flow under certain conditions.