Stochastic effects on phase-space holes and clumps in kinetic systems near marginal stability

The creation and subsequent evolution of marginally-unstable modes have been observed in a wide range of fusion devices. This behaviour has been successfully explained, for a single frequency shifting mode, in terms of phase-space structures known as a 'hole' and 'clump'. Here, w...

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Bibliographic Details
Published in:Nuclear fusion 2018-08, Vol.58 (8), p.82015
Main Authors: Woods, B.J.Q., Duarte, V.N., De-Gol, A.J., Gorelenkov, N.N., Vann, R.G.L.
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
fast ions
hole and clump
kinetic instabilities
mode chirping
nonlinear dynamics
stochasticity
turbulence
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Summary:The creation and subsequent evolution of marginally-unstable modes have been observed in a wide range of fusion devices. This behaviour has been successfully explained, for a single frequency shifting mode, in terms of phase-space structures known as a 'hole' and 'clump'. Here, we introduce stochasticity into a 1D kinetic model, affecting the formation and evolution of resonant modes in the system. We find that noise in the fast particle distribution or electric field leads to a shift in the asymptotic behaviour of a chirping resonant mode; this noise heuristically maps onto radial microturbulence via canonical toroidal momentum scattering, affecting hole and clump formation. While the mechanism allowing for the formation of the hole and clump is coherent, the lifetime of a hole and clump is shown to be highly sensitive to initial conditions, affecting the temporal profile of a single bursting event in mode amplitude.
ISSN:0029-5515
1741-4326
DOI:10.1088/1741-4326/aaa9fd