Direct evidence of <i>E</i> × <i>B</i> flow changes at the onset of resonant magnetic perturbation-driven edge-localized mode crash suppression

Lee, Jae-Hyun; Jeon, Y.M.; In, Y.; Park, G.Y.; Yun, Gunsu; Lee, W.; Kim, M.; Lee, J.H.; Ko, W. H.; Park, H.K.

doi:10.1088/1741-4326/ab167a

Cited by 29 publications

(39 citation statements)

References 46 publications

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“…W • > at the pedestal is ion-diamagnetic direction due to large [32], and therefore modes rotate in the clockwise direction. This similarity of e, †J ‡I and e, is also consistent with the previous studies [32,33].…”

Section: Pbm Simulation Without Rmp Effectsupporting

confidence: 92%

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Nonlinear modeling of the effect of n = 2 resonant magnetic field perturbation on peeling-ballooning modes in KSTAR

et al. 2020

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The impact of n=2 resonant magnetic perturbation (RMP) on the pedestal and peeling-ballooning mode (PBM) is investigated using the nonlinear 3D MHD code JOREK. It is based on the reduced MHD equations (viscos-resistive MHD), and the experimental parameters from the RMP-driven Edge localized mode (ELM) suppression discharge in KSTAR. In this study, n=2 kink-peeling mode was triggered through nonlinear coupling with RMP, and the pedestal is degraded by increased radial transport due to both tearing and kink-peeling response. The ELM mitigation and suppression are observed when RMP of sufficient amplitude is applied. ELM suppression was characterized by spatial locking of mode structure. In the simulation, the ELM suppression is not only due to the degraded pedestal but is also related to the mode coupling between the PBMs and the RMP-induced mode at the plasma edge. The role of PBM locking in mode suppression is suggested in terms of mode coupling.

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Section: Pbm Simulation Without Rmp Effectsupporting

confidence: 92%

“…In this work, we use the data from KSTAR #18594 [33] discharge of n=2 RMP driven ELM suppression in the simulation. The summary of discharge is shown in Figure 1.…”

Section: Ii-2 Input Configurationmentioning

confidence: 99%

Nonlinear modeling of the effect of n = 2 resonant magnetic field perturbation on peeling-ballooning modes in KSTAR

et al. 2020

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“…This apparent hysteresis suggests the bifurcation of magnetic topology. The similar hysteresis relation is also observed in KSTAR [205]. The bifurcation of perpendicular velocity of turbulence which is mainly contributed by E � B flow was found to be directly associated with the bifurcation between ELM suppression and mitigation.…”

Section: Stochastization Of Magnetic Fieldsupporting

confidence: 79%

Bifurcation phenomena in magnetically confined toroidal plasmas

Ida

2020

Advances in Physics: X

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Bifurcation phenomena observed in turbulence and transport, in topology of magnetic field and MHD, and the interplay between turbulence and MHD bifurcation in magnetically confined toroidal plasmas are reviewed. Two types of bifurcation phenomena in turbulent transport are discussed. One is significant change in the magnitude of the diffusion term and the other is a sign flip of non-diffusive term of transport. The bifurcation of diffusion term magnitude causes the transition to a so-called improved mode such as ion-electron root transition, L-mode to H-mode transition, and ITB formation. In contrast, the bifurcation of non-diffusion term sign causes the intrinsic flow reversal, convection reversal of bulk ion, and impurity ions. Two types of bifurcation phenomena in MHD are discussed. One is the bifurcation of static magnetic topology and the other is the bifurcation of MHD instability. The bifurcation of static magnetic topology is observed in between three magnetic topology (nested magnetic flux surface, magnetic island and stochastic magnetic field) in toroidal plasma. The bifurcation of MHD instability is observed as a parity change of MHD oscillation. The bifurcation of the magnetic island states caused by the interplay between turbulence and MHD is also discussed.

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“…Since the poloidal flow speed is likely dominated by the E r x B term, it is logical to conclude that the sudden change of the perpendicular flow speed has to do with the change of E r . It is important to separate this effect from the E r x B physics of the H-mode near the pedestal region which is extremely narrow [133]. As the RMP current is ramped down, amplitude of the turbulence has a long-time delay before it starts decreasing.…”

Section: What Are the New Findings In The Study Of Alfvén Mode Instabmentioning

confidence: 99%

“…Does this implicate recovery of the E r x B? If the sudden bifurcation of the electron flow speed is associated with the E r change [133], it is reasonable to conclude that the time history of the turbulence is not correlated with that of E r . As shown in Figure 31b, the time evolution of the observed turbulence on poloidal plane shows that the level is increasing with broad spectra as it approaches to the flat top of the RMP current ramp-up phase.…”

Section: What Are the New Findings In The Study Of Alfvén Mode Instabmentioning

confidence: 99%

Newly uncovered physics of MHD instabilities using 2-D electron cyclotron emission imaging system in toroidal plasmas

Park

2019

Advances in Physics: X

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Validation of physics models using the newly uncovered physics with a 2-D electron cyclotron emission imaging (ECEi) system for magnetic fusion plasmas has either enhanced the confidence or substantially improved the modeling capability. The discarded "full reconnection model" in sawtooth instability is vindicated and established that symmetry and magnetic shear of the 1/1 kink mode are critical parameters in sawtooth instability. For the 2/ 1 instability, it is demonstrated that the 2-D data can determine critical physics parameters with a high confidence and the measured anisotropic distribution of the turbulence and its flow in presence of the 2/1 island is validated by the modelled potential and gyro-kinetic calculation. The validation process of the measured reversed-shear Alfvéneigenmode (RSAE) structures has improved deficiencies of prior models. The 2-D images of internal structure of the ELMs and turbulence induced by the resonant magnetic perturbation (RMP) have provided an opportunity to establish firm physics basis of the ELM instability and role of RMPs. The importance of symmetry in determining the reconnection time scale and role of magnetic shear of the 1/1 kink mode in sawtooth instability may be relevant to the underlying physics of the violent kink instability of the filament ropes in a solar flare.

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Direct evidence of E × B flow changes at the onset of resonant magnetic perturbation-driven edge-localized mode crash suppression

Cited by 29 publications

References 46 publications

Nonlinear modeling of the effect of n = 2 resonant magnetic field perturbation on peeling-ballooning modes in KSTAR

Nonlinear modeling of the effect of n = 2 resonant magnetic field perturbation on peeling-ballooning modes in KSTAR

Bifurcation phenomena in magnetically confined toroidal plasmas

Newly uncovered physics of MHD instabilities using 2-D electron cyclotron emission imaging system in toroidal plasmas

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