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Start Over Author "Qiu Z" Journal physics of plasmas
8 results on '"Qiu Z"'

1. Effects of energetic particles on zonal flow generation by toroidal Alfvén eigenmode

Author

Qiu, Z, Chen, L, and Zonca, F

Subjects
physics.plasm-ph, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Classical Physics, Fluids & Plasmas
Abstract

Generation of zonal flow (ZF) by energetic particle (EP) driven toroidal Alfvén eigenmode (TAE) is investigated using nonlinear gyrokinetic theory. It is found that nonlinear resonant EP contribution dominates over the usual Reynolds and Maxwell stresses due to thermal plasma nonlinear response. ZF can be forced driven in the linear growth stage of TAE, with the growth rate being twice the TAE growth rate. The ZF generation mechanism is shown to be related to polarization induced by resonant EP nonlinearity. The generated ZF has both the usual meso-scale and micro-scale radial structures. Possible consequences of this forced driven ZF on the nonlinear dynamics of TAE are also discussed.

Published
2016

2. On fast radial propagation of parametrically excited geodesic acoustic mode

Author

Qiu, Z, Chen, L, and Zonca, F

Subjects
physics.plasm-ph, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Classical Physics, Fluids & Plasmas
Abstract

The spatial and temporal evolution of parametrically excited geodesic acoustic mode (GAM) initial pulse is investigated both analytically and numerically. Our results show that the nonlinearly excited GAM propagates at a group velocity which is, typically, much larger than that due to finite ion Larmor radius as predicted by the linear theory. The nonlinear dispersion relation of GAM driven by a finite amplitude drift wave pump is also derived, showing a nonlinear frequency increment of GAM. Further implications of these findings for interpreting experimental observations are also discussed.

Published
2015

5. Cross-code gyrokinetic verification and benchmark on the linear collisionless dynamics of the geodesic acoustic mode

Author

Biancalani, A., primary, Bottino, A., additional, Ehrlacher, C., additional, Grandgirard, V., additional, Merlo, G., additional, Novikau, I., additional, Qiu, Z., additional, Sonnendrücker, E., additional, Garbet, X., additional, Görler, T., additional, Leerink, S., additional, Palermo, F., additional, and Zarzoso, D., additional

Published
2017
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8. Nonlinear dynamics of shear Alfvén fluctuations in divertor tokamak test facility plasmas

Author

Gregorio Vlad, Fulvio Zonca, Sergio Briguglio, Xin Wang, Zhiyong Qiu, Tao Wang, Wang, T., Wang, X., Briguglio, S., Qiu, Z., Vlad, G., and Zonca, F.

Subjects
Physics, Tokamak, Toroid, Divertor, Plasma, Condensed Matter Physics, 01 natural sciences, Physics - Plasma Physics, Spectral line, Outer core, 010305 fluids & plasmas, law.invention, Physics::Plasma Physics, law, Normal mode, Excited state, 0103 physical sciences, Atomic physics, 010306 general physics
Abstract

Following the analysis on linear spectra of shear Alfv\'en fluctuations excited by energetic particles (EPs) in the Divertor Tokamak Test (DTT) facility plasmas [T. Wang et al., Phys. Plasmas 25, 062509 (2018)], in this work, nonlinear dynamics of the corresponding mode saturation and the fluctuation induced EP transport is studied by hybrid magnetohydrodynamic-gyrokinetic simulations. For the reversed shear Alfv\'en eigenmode driven by magnetically trapped EP precession resonance in the central core region of DTT plasmas, the saturation is mainly due to radial decoupling of resonant trapped EPs. Consistent with the wave-EP resonance structure, EP transport occurs in a similar scale to the mode width. On the other hand, passing EP transport is analyzed in detail for toroidal Alfv\'en eigenmode in the outer core region, with mode drive from both passing and trapped EPs. It is shown that passing EPs experience only weak redistributions in the weakly unstable case; and the transport extends to meso-scale diffusion in the strongly unstable case, due to orbit stochasticity induced by resonance overlap. Here, weakly/strongly unstable regime is determined by Chirikov condition for resonance overlap. This work then further illuminates rich and diverse nonlinear EP dynamics related to burning plasma studies, and the capability of DTT to address these key physics., Comment: 32 pages, 20 figures

Published
2019

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