Mode conversion and collisionless absorption of externally driven waves in the lower hybrid frequency range in an inhomogeneous plasma are described through numerical analysis of the locally evaluated linear dispersion relation for a homogeneous plasma. The effects of finite temperature and inhomogeneity of the plasma are emphasized since, according to the linear theory, these effects are responsible for the eventual absorption of the waves by the plasma. The exact forms of the dispersion relations, derived first from the two-fluid equations with an isotropic pressure law and then from the Vlasov equation, are analyzed for plasma parameters applicable to present day tokamaks. The two-fluid theory predicts that a mode conversion to an acoustic wave takes place near the lower hybrid resonance density layer. The Vlasov theory, in addition, predicts that this may be followed by a second mode conversion at a lower density. The results of the Vlasov theory also include electron Landau damping and ion cyclotron harmonic damping.

The linear response of a cold anisotropic plasma to a point source under impulse excitation displays a frequency spectrum having maxima at the two frequencies determined by the resonance cone condition and at the upper hybrid frequency. A laboratory demonstration is reported.

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Behavior of multiple degree of freedom systems having neighboring eigenvalues: Veering of the eigenvalue loci and high mode sensitivity