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Abstract

Mode conversion between the fast and slow electromagnetic waves in the lower hybrid frequency range is considered. This phenomenon determines the accessibility of the lower hybrid resonance to the slow wave, and is also of theoretical interest because the mode coupling differs in certain aspects from cases previously investigated by the authors and others. A second order approximation is used in the mode conversion region leading to Weber's equation from which transmission coefficients are then obtained in various cases. Ray tracing results are recovered for a plasma with a linear density profile in a uniform magnetic field. The effect of including a magnetic field gradient in the calculation is also considered. The second part of the paper provides a justification for the use of Weber's equation. The exact fourth system of O.D.E.s for the problem is set down and a linear transformation, which is an extension of that given by Heading, reveals the second order nature of the coupling process Numerical solutions of the fourth order system yield transmission coefficients in excellent agreement with the second order theory, and also demonstrate that the electric field variation across the mode conversion region is well approximated, via the above transformation, by the second order theory.

Additional information

Authors: WOODS A M, ST. ANDREWS UNIVERSITY (UK);CULHAM LABORATORY, ABINGDON (UK);CAIRNS R A, ST. ANDREWS UNIVERSITY (UK);CULHAM LABORATORY, ABINGDON (UK);LASHMORE DAVIES C N ST. ANDREWS UNIVERSITY (UK), ST. ANDREWS UNIVERSITY (UK);CULHAM LABORATORY, ABINGDON (UK);CULHAM LABORATORY, ABINGDON (UK), ST. ANDREWS UNIVERSITY (UK);CULHAM LABORATORY, ABINGDON (UK)
Bibliographic Reference: WRITE TO THE LIBRARIAN, UKAEA, CULHAM LABORATORY, ABINGDON, OXON, OX14 3DB (UK), MENTIONING REPORT CLM-P759, 1985
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