Theory and observations of magnetic islands

Waelbroeck, F. L.

doi:10.1088/0029-5515/49/10/104025

Cited by 111 publications

(112 citation statements)

References 189 publications

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“…[64]. The effect may be understood as a consequence of the frozen-in law for electrons: since the electrons are unable to cross the separatrix once a magnetic island exceeds the tearing layer width, the existence of an electric field within the separatrix, whether from neutral beams or other causes, implies the presence of a diamagnetic drift that cancels the electric drift [3]. The formation of the pressure-gradient that creates the diamagnetic drift gives rise to a pumpout or a pump-in, according to the sign of the electric field.…”

Section: Role Of Singular Layers In the Plasma Response To Resonant Mmentioning

confidence: 99%

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Role of singular layers in the plasma response to resonant magnetic perturbations

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Abstract. The response of an H-mode plasma to magnetic perturbations that are resonant in the edge is evaluated using a fluid model. With two exceptions, the plasma rotation suppresses the formation of magnetic islands, holding their widths to less than a tenth of those predicted by the vacuum approximation. The two exceptions are at the foot of the pedestal, where the plasma becomes more resistive, and at the surface where the perpendicular component of the electron velocity reverses. The perturbations exert a force on the plasma that is such as to brake the perpendicular component of the electron rotation. In the pedestal, the corresponding Maxwell stress drives the radial electric field in such a way as to accelerate ion rotation. Despite the suppression of the islands, the perturbations give rise to particle fluxes caused by magnetic flutter, with a negligible contribution from E×B convection. In the pedestal, the fluxes are such as to reduce the density.

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Section: Role Of Singular Layers In the Plasma Response To Resonant Mmentioning

confidence: 99%

“…Magnetic perturbations are said to be resonant when they induce a finite electromotive force on closed field-lines lying inside the plasma [3]. Resonant magnetic perturbations can be produced by currents flowing in coils external to the plasma, or by a saturated intrinsic mode such as the edge harmonic oscillation (EHO) [4,5,6].…”

Section: Introductionmentioning

confidence: 99%

Role of singular layers in the plasma response to resonant magnetic perturbations

et al. 2012

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“…1 Instability which excites magnetic islands is called the tearing mode. [2][3][4][5] Even if the intrinsic tearing mode is stable, magnetic islands are produced by external resonant magnetic perturbation (RMP) through the mechanism of the forced magnetic reconnection.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear stability of magnetic islands in a rotating helical plasma

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Linear and nonlinear wave propagation in weakly relativistic quantum plasmas Phys. Plasmas 20, 012114 (2013) Time-domain simulation of nonlinear radiofrequency phenomena Phys. Plasmas 20, 012116 (2013) Small amplitude nonlinear electron acoustic solitary waves in weakly magnetized plasma Phys. Plasmas 20, 012113 (2013) Dust-acoustic shock formation in dusty plasmas with non-thermal ions Phys. Plasmas 20, 013704 (2013) Additional information on Phys. Plasmas Coexistence of the forced magnetic reconnection by a resonant magnetic perturbation (RMP) and the curvature-driven tearing mode is investigated in a helical (stellarator) plasma rotated by helical trapped particle-induced neoclassical flows. A set of Rutherford-type equations of rotating magnetic islands and a poloidal flow evolution equation is revisited. Using the model, analytical expressions of criteria of spontaneous shrinkage (self-healing) of magnetic islands and sudden growth of locked magnetic islands (penetration of RMP) are obtained, where nonlinear saturation states of islands show bifurcation structures and hysteresis characteristics. Considering radial profile of poloidal flows across magnetic islands, it is found that the self-healing is driven by neoclassical viscosity even in the absence of micro-turbulence-induced anomalous viscosity.

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“…Magnetic islands, generated by the tearing mode, have the effect of breaking the axisymmetric properties of the equilibrium, and can have a detrimental effect on the plasma confinement due to the radial component of the magnetic field that they introduce [1][2][3].…”

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On the dynamics of vortex modes within magnetic islands

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Recent work investigating the interaction of magnetic islands with micro-turbulence has uncovered the striking observation of large scale vortex modes forming within the island structure [W.A.Hornsby et al., Phys. Plasmas 17 092301 (2010)]. These electrostatic vortices are found to be the size of the island and are oscillatory. It is this oscillatory behaviour and the presence of turbulence that leads us to believe that the dynamics are related to the Geodesic Acoustic Mode (GAM), and it is this link that is investigated in this paper.Here we derive an equation for the GAM in the MHD limit, in the presence of a magnetic island modified three-dimensional axisymmetric geometry. The eigenvalues and eigenfunctions are calculated numerically and then utilised to analyse the dynamics of oscillatory large-scale electrostatic potential structures seen in both linear and non-linear

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Theory and observations of magnetic islands

Cited by 111 publications

References 189 publications

Role of singular layers in the plasma response to resonant magnetic perturbations

Role of singular layers in the plasma response to resonant magnetic perturbations

Nonlinear stability of magnetic islands in a rotating helical plasma

On the dynamics of vortex modes within magnetic islands

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