Unstable ion cyclotron harmonic waves generated by inhomogeneity and the ion beam in an ion-beam-plasma system

In an ion-beam-inhomogeneous-plasma system, when the drift. frequency omega* exceeds a harmonic of the ion cyclotron frequency nomega(ci), ion cyclotron harmonic waves are excited via the plasma inhomogeneity. These waves are strongly enhanced by ion-beam injection parallel to the magnetic field. As the plasma inhomogeneity is increased, the number of unstable modes increases as does their amplitude. Ion cyclotron harmonic waves with frequencies up to 4omega(ci) are observed experimentally; at least five modes become unstable, and these unstable waves have different, azimuthal mode. numbers l = 1 or 2. The dispersion relations of observed multiple ion cyclotron harmonic waves agree well with the theoretical ones, taking into account. the plasma inhomogeneity and the ion beam.