MHD leaky waves in a layered plasma. I: Theory. II: Mechanism of leakage. III: Numerical solutions (Q1303667)

The authors investigate the stability of compressible perfectly conducting plasma layers that are imbedded in two-dimensional varying magnetic field. The investigation is limited by the linear stability analysis. The authors find stationary magnetohydrodynamic equilibrium states for three-layer plasma. The matching of the perturbations of two uniform media at their interface is described by a matrix equation. Using the standard technique, the authors obtain four different dispersion relations. In part I the general theory of MHD leaky waves is presented. Part II is devoted to the discussion of the physical mechanism of leakage. Four basic leakage mechanisms are established: surface modes, single interface modes, trapped waves, and lost insulation leakage modes. All mechanisms can be clearly separated only in the limiting cases. The complex branches of the roots of the dispersion relation correspond to leaky waves, and in general case it is not possible to classify the waves. Part III presents numerical calculations of complex frequencies of leaky waves. It is shown that the wave spectra consist of an infinite set of branches. Several of four leakage mechanisms can operate in real plasma configurations. Since no restrictions are imposed on the configuration, the presented methods allow to investigate arbitrary cases.