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Wave-particle interactions in electrostatic waves in an inhomogeneous medium

Published online by Cambridge University Press:  13 March 2009

D. Nunn
D. Nunn
Affiliation:
Imperial College of Science and Technology, London
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Abstract

The system studied is that of a narrow-band electrostatic wave packet in a collision-free plasma. Inhomogeneous effects are represented by a wave-number, which varies linearly with distance. The system is excited by a weak resonant beam, and, to first order in a smallness parameter associated with the weakness of the beam, the resonant-particle distribution function and charge densities are calculated. It is found that second-order resonant particles become stably trapped in the wave, and, after a few trapping periods, make a dominant contribution to the resonant particle charge density. The growth rate due to the resonant beam was found to increase linearly with trapping time, and typically a pulse which traps particles for n trapping periods exhibits a growth rate ˜ n times the linear Landau value. Furthermore, a reactive component of charge density was found that was able to cause a steady change in wave frequency and wave-number. These features of large growth rates and changing frequency should appear in parallel problems involving other wave types. An obvious application is that of VLF emissions in the whistler mode.

Type
Research Article
Information
Journal of Plasma Physics , Volume 6 , Issue 2 , October 1971 , pp. 291 - 307
Copyright
Copyright © Cambridge University Press 1971

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References

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