Electrostatic ion-cyclotron waves in a plasma with negative ions

Electrostatic ion-cyclotron (EIC) waves have been investigated in plasmas containing K+ positive ions, electrons, and SF-6 negative ions. Two EIC wave modes are generally present, the K+ and SF-6 modes. Their frequencies increase with increasing ε, the percentage of negative ions, while the critical electron drift velocities for excitation of either mode decrease with increasing ε. The observations are discussed on the basis of available theories