Stability of Electrostatic Ion Cyclotron Harmonic Waves in a Multi-ion Plasma

Electrostatic ion cyclotron (EIC) waves in a multi-ion plasma is studied. Electrons and hydrogen ions drifting with velocities and, respectively, along the ambient magnetic field and positively and negatively charged oxygen ions constitute the plasma under consideration. This composition very well approximates the plasma environment around a comet. Analytical expressions for the frequency and growth / damping rate of the EIC waves around the higher harmonics of hydrogen ion gyrofrequency have been derived. The EIC waves propagate at frequencies around the harmonics of the hydrogen ion gyrofrequency and the wave growth decreases rapidly for higher harmonics. We find that, the wave can be driven unstable by the hydrogen ion drift velocity alone, at small as well as electron drift velocity at large. Also, the growth rate is dependent on the densities and temperature anisotropies of the various constituent ions.