Electrostatic ion cyclotron instabilities in negative ion plasmas

The effect of negative ions on the collisionless electrostatic ion cyclotron instability (EICI) is investigated analytically and numerically. The singly ionized negative ion species has mass greater than or equal to the mass of the singly ionized positive ion species. Standard linear Vlasov theory is used to estimate the critical electron drift velocity. It is shown that the critical drifts for the excitation of both the light and heavy ion EIC modes decrease as the relative density of negative ions increases. Our results are compared with available negative ion plasma experiments concerning the EICI, and possible applications to experiments in the ionosphere are briefly discussed. (C) 1996 American Institute of Physics.