Wave Propagation in Non-Uniform Plasmas

Diver, Declan Andrew (1986) Wave Propagation in Non-Uniform Plasmas. PhD thesis, University of Glasgow.

Abstract

This thesis concentrates on phenomena associated with waves propagating in an inhomogeneous medium, in particular the transmission and reflection of wave motion in a non-uniform plasma, and the process of exciting secondary wave motion, termed mode conversion. To this end, a thorough treatment of the phase integral, or WKBJ, method is given in Chapter II, together with a careful statement of under what circumstances it is applicable, and, if so, to what accuracy. As a novel example of this powerful technique being applied in a specific physical context, WKBJ theory is used in Chapter III to solve for the transmission characteristics of an acoustic guide with varying cross-section. Building on this experience, the phenomenon of mode conversion is defined in Chapter IV, and a critical review is undertaken of the various historical and contemporary approaches to quantifying this effect. Specific examples are cited as evidence of the inadequacy of the reverse Fourier transform technique, including a complete solution of the same non-uniform waveguide problem using this method. The result is contrasted with the previous self-consistent analysis in support of the contention that such reverse transforms are not generally correct. Since most mode conversion theories depend to some extent on the concept of a spatially dependent dispersion relation, Chapter V embarks on a self-consistent analysis of particular mode conversion events, deriving the coupling directly from the behaviour of the eigenvalues of the governing ordinary differential equation. Such analysis recovers some of the more desirable features of the other theories, but in a more rigorous mathematical setting. Finally, wave propagation in a non-uniform mhd fluid plasma is studied, using only the appropriate fluid equations with the inhomogeneity present at the earliest possible stage. Computer algebra is used to perform the necessary algebraic manipulations, and full details are given in Chapter VI. Extra physical effects of interest concerning the Alfven resonant layer are revealed. Chapter VII summarises the conclusions, and suggests further work in the field.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Plasma physics
• Date of Award: 1986
• Depositing User: Enlighten Team
• Unique ID: glathesis:1986-77407
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jan 2020 09:09
• Last Modified: 14 Jan 2020 09:09
• URI: https://theses.gla.ac.uk/id/eprint/77407