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The extension of gyrokinetic theory to arbitrary frequencies is used to study cyclotron absorption in a straight magnetic field with a perpendicular, linear gradient in strength. The analysis includes the effects of magnetic field variation across the Larmor orbit, and is restricted to propagation perpendicular to the field. It yields the following results for propagation into the field gradient. The standard optical depths for the fundamental O-mode and second harmonic X-mode resonances are obtained from absorption profiles without invoking relativistic mass variation. The compressional Alfven wave is shown to undergo perpendicular cyclotron damping at the fundamental minority resonance in a two ion species plasma and at second harmonic resonance in a single ion species plasma. Ion Bernstein waves propagating into the second harmonic resonance are no longer unattenuated, but are increasingly damped as they approach the resonance. It is shown how the kinetic power flow affects absorption profiles, yielding information previously obtainable only from full-wave theory. In all cases, the perpendicular cyclotron damping arises from the inclusion of magnetic field variation across the Larmor orbit.

Additional information

Authors: LASHMORE-DAVIES C N, Culham Laboratory, Abingdon, Oxon. (GB);DENDY R O, Culham Laboratory, Abingdon, Oxon. (GB)
Bibliographic Reference: Report: CLM-P850 EN (1988)
Availability: Available from the Librarian, UKAEA, Culham Laboratory, Abingdon, Oxon. OX14 3DB (GB)
Record Number: 198910340 / Last updated on: 1994-12-01
Original language: en
Available languages: en