Stochastic fluctuation and transport of tokamak edge plasmas with the resonant magnetic perturbation field

Choi, M.; Kwon, Jae-Min; Kim, Juhyung; Rhee, T.; Bak, J. G.; Shin, Giwook; Jhang, Hogun; Kim, Kimin; Yun, Gunsu; Kim, Minwoo; Kim, SangKyeun; Kaang, Helen H.; Park, Jong‐Kyu; Lee, Hyung Ho; In, Y.; Lee, Jae-Hyun; Kim, Minho; Park, Byeongho; Park, Hyeon K.

doi:10.48550/arxiv.2102.10733

Cited by 3 publications

(6 citation statements)

References 38 publications

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“…This offers the possibility of reconciling the decrease in complexity/predictability observed in Ref. [33] with the increase in bicoherence also observed. Finally, extension of this analysis to a kinetic description of microinstabilities should be considered.…”

Section: Conclusion and Discussionsupporting

confidence: 62%

“…Experimental studies of such fine scale fluctuation dynamics are understandably challenging. An interesting and relevant result was recently reported by Choi et al [33], who compared the change in pedestal temperature fluctuation predictability (as deduced from Jensen-Shannon entropy) with RMP switched on and off. These studies focused on the putative stochastic region at the edge of RMP-induced islands in the pedestal.…”

Section: Conclusion and Discussionmentioning

confidence: 72%

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Instability and Turbulent Relaxation in a Stochastic Magnetic Field

Cao¹,

Diamond²

2021

Preprint

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An analysis of instability dynamics in a stochastic magnetic field is presented for the tractable case of the resistive interchange. Externally prescribed static magnetic perturbations convert the eigenmode problem to a stochastic differential equation, which is solved by the method of averaging. The dynamics are rendered multi-scale, due to the size disparity between the test mode and magnetic perturbations. Maintaining quasi-neutrality at all orders requires that small-scale convective cell turbulence be driven by disparate scale interaction. The cells in turn produce turbulent mixing of vorticity and pressure, which is calculated by fluctuation-dissipation type analyses, and are relevant to pump-out phenomena. The development of correlation between the ambient magnetic perturbations and the cells is demonstrated, showing that turbulence will 'lock on' to ambient stochasticity. Magnetic perturbations are shown to produce a magnetic braking effect on vorticity generation at large scale.Detailed testable predictions are presented. The relations of these findings to the results of available simulations and recent experiments are discussed. I. INTRODUCTIONThe dynamics of instability, relaxation, and turbulence are (taken collectively) fundamental to magnetic confinement physics. Here, 'relaxation' includes the evolution of plasma free energy (in the presence of sources and sinks), and the resulting transport [1]. Relaxation determines plasma confinement and possible bifurcations between different states thereof [2].Recently, a new element has been added to this already challenging problem. Good confinement is no longer deemed sufficient. Rather, good confinement must be achieved along with

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Section: Conclusion and Discussionsupporting

confidence: 62%

Section: Conclusion and Discussionmentioning

confidence: 72%

Instability and Turbulent Relaxation in a Stochastic Magnetic Field

Cao¹,

Diamond²

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Here, the presence of the stochastic field and the modulationally generated small-scale convective cells potentially open the possibility of increased nonlinear transfer, by increasing the number of triad interactions. This offers the possibility of reconciling the decrease in complexity/predictability observed in [35] with the increase in bicoherence also observed. Finally, extension of this analysis to a kinetic description of microinstabilities should be considered.…”

Section: Conclusion and Discussionmentioning

confidence: 68%

“…Experimental studies of such fine scale fluctuation dynamics are understandably challenging. An interesting and relevant result was recently reported by Choi et al [35], who compared the change in pedestal temperature fluctuation predictability (as deduced from Jensen-Shannon entropy) with RMP switched on and off. These studies focused on the putative stochastic region at the edge of RMP-induced islands in the pedestal.…”

Section: Conclusion and Discussionmentioning

confidence: 72%

Instability and turbulent relaxation in a stochastic magnetic field

Cao

Diamond

2022

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

An analysis of instability dynamics in a stochastic magnetic ﬁeld is presented for the tractable case of the resistive interchange. Externally prescribed static magnetic perturbations convert the eigenmode problem to a stochastic diﬀerential equation, which is solved by the method of averaging. The dynamics are rendered multi-scale, due to the size disparity between the test mode and magnetic perturbations. Maintaining quasi-neutrality at all orders requires that small-scale convective cell turbulence be driven by disparate scale interaction. The cells in turn produce turbulent mixing of vorticity and pressure, which is calculated by ﬂuctuation-dissipation type analyses, and are relevant to pump-out phenomena. The development of correlation between the ambient magnetic perturbations and the cells is demonstrated, showing that turbulence will ‘lock on’ to ambient stochasticity. Magnetic perturbations are shown to produce a magnetic braking eﬀect on vorticity generation at large scale. Detailed testable predictions are presented. The relations of these ﬁndings to the results of available simulations and recent experiments are discussed.

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“…The correlation ⟨ br ṽr ⟩ is also calculated explicitly. This correlation can explain the decrease in Jensen-Shannon complexity and predictability observed during the RMP ELM suppression phase on KSTAR [80]. The readers can see [74,75] for more details.…”

Section: Effects Of Stochastic Magnetic Fields On Turbulencementioning

confidence: 76%

Theory of mean E × B shear in a stochastic magnetic field: ambipolarity breaking and radial current

Guo

Jiang²,

Diamond³

et al. 2022

Plasma Phys. Control. Fusion

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The mean E×B shear in a stochastic magnetic field is calculated, using the radial force balance relation and transport equations. This analysis is relevant to the L→H transition with resonant magnetic perturbations (RMP), and special focus is placed upon the physics of non-ambipolar transport and radial current. The key physical process is the flow of fluctuating current along wandering magnetic fields. The increments in poloidal and toroidal rotation, density and ion pressure are calculated. The radial envelope of the magnetic perturbations inside the plasma defines a new scale l_env, which is the characteristic scale of the magnetic fluctuation intensity profile. The net particle outflow due to stochastic magnetic fields is calculated and is determined by the net radial current through the separatrix. Implications for the L→H transition are discussed.

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Stochastic fluctuation and transport of tokamak edge plasmas with the resonant magnetic perturbation field

Cited by 3 publications

References 38 publications

Instability and Turbulent Relaxation in a Stochastic Magnetic Field

Instability and Turbulent Relaxation in a Stochastic Magnetic Field

Instability and turbulent relaxation in a stochastic magnetic field

Theory of mean E × B shear in a stochastic magnetic field: ambipolarity breaking and radial current

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