Article Dans Une Revue Physics of Plasmas Année : 2013

Effects of collisions on energetic particle-driven chirping bursts

Maxime Lesur

Résumé

In the presence of an energetic particle population in a dissipative plasma, self-trapped structures in phase-space (holes and clumps) emerge from nonlinear wave-particle interactions. Their dynamics can lead to a nonlinear continuous shifting of the wave frequency (chirping). The effects of collisions on chirping characteristics are investigated, with a one-dimensional kinetic model. Existing analytic theory is extended to account for Krook-like collisions, which quantitatively explains a significant departure from widely accepted square-root time dependency. Relaxation oscillations, associated with chirping bursts, are investigated in the presence of dynamical friction and velocity-diffusion. The period increases with decreasing drag and weakly increases with decreasing diffusion. The mechanism is clarified with a simple semi-analytic model of hole/clump pair, which satisfies a Fokker-Planck equation. The model shows that the linear growth rate cannot be obtained simply by fitting an exponential to the amplitude time-series. V C 2013 AIP Publishing LLC.

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hal-01969744 , version 1 (14-01-2019)

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Maxime Lesur. Effects of collisions on energetic particle-driven chirping bursts. Physics of Plasmas, 2013, 20, pp.055905. ⟨10.1063/1.4804644⟩. ⟨hal-01969744⟩
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