Effect of dynamical friction on nonlinear energetic particle modes

Journal Article · Wed Sep 15 04:00:00 EDT 2010 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3486535· OSTI ID:21432274

Lilley, M K ^[1]; Breizman, B N ^[2]; Sharapov, S E ^[3]

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1. Department of Earth and Space Sciences, Chalmers University of Technology, 41296 Goeteborg (Sweden)
2. Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States)
3. EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)

A fully nonlinear model is developed for the bump-on-tail instability including the effects of dynamical friction (drag) and velocity space diffusion on the energetic particles driving the wave. The results show that drag provides a destabilizing effect on the nonlinear evolution of waves. Specifically, in the early nonlinear phase of the instability, the drag facilitates the explosive scenario of the wave evolution, leading to the creation of phase space holes and clumps that move away from the original eigenfrequency. Later in time, the electric field associated with a hole is found to be enhanced by the drag, whereas for a clump it is reduced. This leads to an asymmetry of the frequency evolution between holes and clumps. The combined effect of drag and diffusion produces a diverse range of nonlinear behaviors including hooked frequency chirping, undulating, and steady state regimes. An analytical model is presented, which explains the aforementioned diversity. A continuous production of hole-clump pairs in the absence of collisions is also observed.

• OSTI ID: 21432274
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 9 Vol. 17; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DRAG
FRICTION
INSTABILITY
MATHEMATICAL SPACE
NONLINEAR PROBLEMS
PHASE SPACE
PLASMA INSTABILITY
PLASMA SIMULATION
PLASMA WAVES
SIMULATION
SPACE