Magnetohydrodynamical Leaky Waves in a Layered Plasma: II. Mechanisms of Leakage

A. G. GONZÁLEZ; J. GRATTON; S. FARINA

ASTROPHYSICS AND SPACE SCIENCE

Kluwer

Año: 1997 vol. 256 p. 297 - 301

0004-640X

The application of Fourier analysis to study leaky waves has the advantage of simplicity, but it is not clear why the complex roots of the dispersion relations represent leaky waves, nor how the leakage occurs. We investigate the different kinds of leakage that can occur in a three layer plasma, and to which Fourier pseudomodes they are associated. We find four basic mechanisms, called ``surface mode ...'', ``single interface ...'', ``trapped wave ...'' and ``lost insulation leakage''. These mechanisms appear in pure form only near certain limiting cases, in which the parameters of the problem take some special values. As soon as the parameters depart significantly from the limiting values, the behavior of the leaky wave complicates and mixtures of the mechanisms occur, in varying amounts. In consequence different points of the same complex branch of the spectrum may correspond to different mechanisms. All the complex branches of the spectrum correspond to leaky waves, but in general it is not possible to classify them according to type of leakage, except close to a limiting case. Since in a three layer configuration there are many of these, the spectrum of leaky waves is very complicated.