Linear and nonlinear stability of drift-tearing mode

Yu, Q.

doi:10.1088/0029-5515/50/2/025014

Cited by 43 publications

(76 citation statements)

References 31 publications

(136 reference statements)

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“…It should be mentioned that the diamagnetic drift has not been included in our model, which is important in determining the tearing mode stability for high β plasmas with large electron pressure gradient [11][12][13][14][15][16][48][49][50]. Linear tearing modes are found to be completely stabilized for a sufficiently large electron diamagnetic drift frequency [11,[48][49]. In the nonlinear phase the ion polarization current associated with diamagnetic drifts leads to a threshold for the onset of neoclassical tearing modes [11][12][13][14][15][16].…”

Section: Numerical Modelingmentioning

confidence: 99%

“…Also, the effect of diamagnetic drifts is weak due to the pressure flattening across a large island [11].…”

Section: Numerical Modelingmentioning

confidence: 99%

“…When the island width is not too large, however, a variety of stabilizing or destabilizing mechanisms are involved, such as the ion polarization current [11][12][13][14][15][16] and the plasma viscosity [14,17]. The classical tearing mode stability in low β plasmas has been investigated in [18].…”

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confidence: 99%

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Effect of externally applied resonant magnetic perturbations on resistive tearing modes

Ren

et al. 2012

Nucl. Fusion

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127

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Section: Numerical Modelingmentioning

confidence: 99%

“…Also, the effect of diamagnetic drifts is weak due to the pressure flattening across a large island [11].…”

Section: Numerical Modelingmentioning

confidence: 99%

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Effect of externally applied resonant magnetic perturbations on resistive tearing modes

Ren

et al. 2012

Nucl. Fusion

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127

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“…A cylindrical, two fluids, non-linear MHD code is used to simulate the mode triggering [13,14]. Simulations use the measured experimental plasma parameters ( , and a bootstrap current fraction of 10%).…”

Section: E-mail Address: Valentinigochine@ippmpgdementioning

confidence: 99%

Conversion of the dominantly ideal perturbations into a tearing mode after a sawtooth crash

et al. 2014

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Forced magnetic reconnection is a topic of common interest in astrophysics, space science and magnetic fusion research. The tearing mode formation process after sawtooth crashes implies the existence of this type of magnetic reconnection and is investigated in great detail in the ASDEX Upgrade tokamak. The sawtooth crash provides a fast relaxation of the core plasma temperature and can trigger a tearing mode at a neighbouring resonant surface. It is demonstrated for the first time that the sawtooth crash leads to a dominantly ideal kink mode formation at the resonant surface immediately after the sawtooth crash. Local measurements show that this kink mode transforms into a tearing mode on a much longer timescale Magnetic reconnection is one of the fundamental processes in magnetized plasmas and central to the understanding of the conversion of magnetic into thermal and kinetic energy in astrophysics, space science and magnetic confinement research. Such plasmas are often nearly collisionless, and the reconnection rates are thus much shorter than predicted by resistive MHD theory. The main difference between astrophysical and magnetic confinement plasmas is the existence of a strong magnetic guide field in the latter case [1]. This paper deals with forced magnetic reconnection in magnetic fusion plasmas. In tokamak plasmas, large sawtooth crashes typically produce fast relaxations of the core plasma density and temperature and provide the drive for magnetic reconnection at the neighbouring resonant surfaces with safety factor q=m/n, where m and n are integer numbers and represent the poloidal and toroidal mode numbers, respectively. Magnetic reconnection rearranges the magnetic topology at the resonant surface. It can start either from noise perturbations if the gradient of the plasma current at the resonant surface provides the drive for a tearing mode [2], or it requires an external drive at the start. The second situation is more common for neoclassical tearing modes (NTMs), which require a seed island to grow. The drive for the tearing mode is usually provided by background MHD instabilities (sawteeth, ELMs, etc.) [3,4,5]. When the critical island width is reached, the pressure profile becomes flat within the island, and the neoclassical drive takes over. Small islands are not able to provide significant pressure flattening and might be driven by other mechanisms [6,7]. In this paper, only the mechanism of the seed island formation by strong internal drive due to sawteeth is investigated in detail. This type of tearing mode formation is considered to be one of the most dangerous for future fusion reactors like ITER [8], because large sawteeth provide the strongest internal magnetic perturbations compared to other possible triggers and are able to trigger the mode already at very small normalized pressure values [3,4]. Previous observations from different tokamaks, for example from JET [9] or TCV [10], report large island widths directly after the crash based on analysis of magnetic and SXR measurements. Such ...

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“…Recent research [18] has shed considerable light on the hitherto poorly understood physical mechanism that underlies RMP-induced ELM suppression in H-mode tokamak discharges. In particular, computer simulations (made using the cylindrical, multi-harmonic, five-field, nonlinear, initial-value code, TM1 [19,20,21]) of RMPinduced ELM suppression experiments performed on the DIII-D tokamak conclude that the density pump-out phenomenon is associated with the formation of a locked magnetic island chain at the bottom of the pedestal, whereas the mode penetration phenomenon is associated with the formation of a locked magnetic island chain at the top of the pedestal.…”

Section: Recent Advances In Theory Of Rmp-generated Elm Suppressionmentioning

confidence: 99%

Theory of edge localized mode suppression by static resonant magnetic perturbations in the DIII-D tokamak

Fitzpatrick

2020

Physics of Plasmas

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An analytic theory of edge localized mode (ELM) suppression in an H-mode tokamak plasma via the application of a static, externally generated, resonant magnetic perturbation (RMP) is presented. This theory is based on the plausible hypothesis that mode penetration at the top of the pedestal is a necessary and sufficient condition for the RMP-induced suppression of ELMs. The theory also makes use of a number of key insights gained in a recent publication (Fitzpatrick R 2019). The first insight is that the response of the plasma to a particular helical component of the RMP, in the immediate vicinity of the associated resonant surface, is governed by nonlinear magnetic island physics, rather than by linear layer physics. The second insight is that neoclassical effects play a vital role in the physics of RMP-induced ELM suppression. The final insight is that plasma impurities play an important role in the physics of RMPinduced ELM suppression. The theory presented in this paper is employed to gain a better understanding ELM suppression in DIII-D and ITER H-mode discharges. It is found that ELM suppression is only possible when q 95 takes values that lie in certain narrow windows. Moreover, the widths of these windows decrease with increasing plasma density. Assuming a core plasma rotation of 20 krad/s, the window width for a model ITER H-mode discharge is found to be similar to, but slightly smaller than, the window width in a typical DIII-D H-mode discharge.

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Linear and nonlinear stability of drift-tearing mode

Cited by 43 publications

References 31 publications

Effect of externally applied resonant magnetic perturbations on resistive tearing modes

Effect of externally applied resonant magnetic perturbations on resistive tearing modes

Conversion of the dominantly ideal perturbations into a tearing mode after a sawtooth crash

Theory of edge localized mode suppression by static resonant magnetic perturbations in the DIII-D tokamak

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