Effects of the fast wave on the drift-cyclotron loss-cone mode

Particle orbits in the presence of the fast wave fields are calculated. It is found that the resonant interaction of ions with the wave can be neglected at ω₀ = 2ω_ci, provided that the wave electric field strength is less than a critical value E_c( = 4k _∥Tle). The dominant effect on the dispersion relation of the drift-cyclotron loss-cone mode is thus found to be due to the nonresonant effects of the wave on electrons and ions. It is found that a fast wave with ω₀ = 2ω_ci destabilizes the mode. For ω₀<2ω_ci, fast waves can stabilize the mode for certain values of the plasma β which is calculated numerically.