Quasi-monochromatic wave-particle interactions in magnetospheric plasmas |
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| Authors: | D Le Quéau A Roux |
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| Institution: | 1. CRPE/CNET/CNRS, Issy-les-Moulineaux, France
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| Abstract: | The natural waves observed within magnetospheres are often emitted over a very narrow spectral range. They thus can interact coherently with the charged particles forming the weakly collisional magnetospheric plasmas. In this review some aspects of these quasi-coherent Wave Particle Interactions, usually known as trapping processes, are underlined. A particular emphasis is here put on the situation effectively encountered within natural plasmas. Hence, the effects of plasma inhomogeneities on the resonant WPI are thoroughly studied. We focus on three effects: - The inhomogeneity of the medium changes the wave number and correspondingly the relative phase between the wave and the particle's motion. Thus, resonant conditions cannot be fulfilled over a large wave path, which tends to decrease the efficiency of the WPI. On the other hand, this effect leads a monochromatic wave to interact with a larger set of charged particles, which tends to restore a quasi linear-like diffusion process.
- Even when trapping occurs, the inhomogeneity changes the saturation level of the kinetic instabilities.
- Trapping can then be an efficient acceleration process.
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