Large-mode-number magnetohydrodynamic instability driven by sheared flows in a tokamak plasma with reversed central shear

Bierwage, Andreas; Yu, Q.; Günter, S.

doi:10.1063/1.2435319

Cited by 36 publications

(40 citation statements)

References 19 publications

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“…Due to mutual interaction between the two resonant surfaces, the DTM is a much stronger instability than the single tearing mode. The dynamic properties of the DTM for different magnetohydrodynamical (MHD) models have been widely studied under various conditions, such as external shear flow, [9][10][11] bootstrap current, 12 anomalous electron viscosity, 13 and collisionless effects. [14][15][16] Recently, it is suggested that the internal transport barrier may be related to the strong shear flows associated with the DTM.…”

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confidence: 99%

Nonlinear evolution of double tearing mode with guiding magnetic field

Zhang

2011

Physics of Plasmas

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Nonlinear dynamic evolution of the double tearing mode (DTM) with a guiding magnetic field (B y0 ) is investigated by magnetohydrodynamical numerical simulation. The dynamic process of DTM depends weakly on the guiding field in the weak guiding field regime (B y0 1), but is suppressed by a strong guiding field (B y0 > 2). During the explosive nonlinear phase, the maximum reconnection rate (c max ) increases weakly with the increase of the resistivity as c max $ g 0:06 for B y0 1, but for B y0 > 2, c max is nearly independent of the resistivity. The maximum reconnection rate in the explosive growth phase increases with increase of the initial current sheet separation. A secondary tearing instability is observed at moderate current sheet separation. A strong guiding field suppresses the formation of a secondary island. Based on the simulation results, it is found that the secondary tearing instability occurs only when the length-tothickness aspect ratio of the reconnection region exceeds about 20.

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confidence: 99%

Nonlinear evolution of double tearing mode with guiding magnetic field

Zhang

2011

Physics of Plasmas

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“…In the linear phase and in the slab geometry, plasma flow shear is found to either increase or decrease the linear growth rate, depending on the plasma viscosity, the magnetic shear and the strength of flow shear. 8,9 When the velocity shear is strong enough, it will give rise to short wave-length Kelvin-Helmholtz (KH) instabilities [10][11][12] and excitation of Alfvé n resonances. [13][14][15] In the nonlinear phase, the flow shear is found to decrease the saturated island width 16 and leads to deformation of magnetic island.…”

Section: Introductionmentioning

confidence: 99%

Linear and nonlinear effect of sheared plasma flow on resistive tearing modes

2014

Physics of Plasmas

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Abstract. The effect of sheared plasma flow on the m/n = 2/1 tearing mode is studied numerically (m and n are the poloidal and toroidal mode numbers). It is found that in the linear phase the plasma flow with a weak or moderate shear plays a stabilizing effect on tearing mode. However, the mode is driven to be more unstable by sufficiently strong sheared flow when approaching the shear Alfvé n resonance (AR). In the nonlinear phase, a moderate (strong) sheared flow leads to a smaller (larger) saturated island width. The stabilization of tearing modes by moderate shear plasma flow is enhanced for a larger plasma viscosity and a lower Alfvé n velocity. It is also found that in the nonlinear phase AR accelerates the plasma rotation around the 2/1 rational surface but decelerates it at the AR location, and the radial location satisfying AR spreads inwards towards the magnetic axis.

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“…The reason for choosing these three rotation profiles is that they have different shear amplitudes and signs at rational surfaces . This is a very important research area in terms of rotational stabilization of MHD instabilities in fusion plasmas (Chu 1998; Bierwage, Yu & Günter 2007; Chapman et al. 2011, 2012; Wahlberg, Graves & Chapman 2013).…”

Section: The Equilibrium Profiles and The Rotation Profilesmentioning

confidence: 99%

“…At present, two mainstream methods are envisaged for the RWM stabilization. One is the active control technique utilizing magnetic coil systems (Fransson et al 2000;Bondeson et al 2001;Liu et al 2004Liu et al , 2005aLiu et al ,b, 2009Liu et al , 2010Drake et al 2005;Gregoratto et al 2005;Martin et al 2009). The other can be called the passive control method, largely relying on additional energy damping often associated with the toroidal flow of the plasma.…”

Section: Introductionmentioning

confidence: 99%

Effects of parallel sound wave damping and drift kinetic damping on the resistive wall mode stability with various plasma rotation profiles

Liu

2015

J. Plasma Phys.

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The effect of a parallel viscous force induced damping and the magnetic precessional drift resonance induced damping on the stability of the resistive wall mode (RWM) is numerically investigated for one of the advanced steady-state scenarios in international thermonuclear experimental reactor (ITER). The key element of the investigation is to study how different plasma rotation profiles affect the stability prediction. The single-fluid, toroidal magnetohydrodynamic (MHD) code MARS-F (Liu et al., Phys. Plasmas, vol. 7, 2000, p. 3681) and the MHD–kinetic hybrid code MARS-K (Liu et al., Phys. Plasmas, vol. 15, 2008, 112503) are used for this purpose. Three extreme rotation profiles are considered: (a) a uniform profile with no shear, (b) a profile with negative flow shear at the $q=2$ rational surface ($q$ is the equilibrium safety factor), and (c) a profile with positive shear at $q=2$. The parallel viscous force is found to be effective for the mode stabilization at high plasma flow speed (about a few percent of the Alfven speed) for the no shear flow profile and the negative shear flow profile, but the stable domain does not appear with the positive shear flow profile. The predicted eigenmode structure is different with different rotation profiles. With a self-consistent inclusion of the magnetic precession drift resonance of thermal particles in MARS-K computations, a lower critical flow speed, i.e. the minimum speed needed for full suppression of the mode, is obtained. Likewise the eigenmode structure is also modified by different rotation profiles in the kinetic results.

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Large-mode-number magnetohydrodynamic instability driven by sheared flows in a tokamak plasma with reversed central shear

Cited by 36 publications

References 19 publications

Nonlinear evolution of double tearing mode with guiding magnetic field

Nonlinear evolution of double tearing mode with guiding magnetic field

Linear and nonlinear effect of sheared plasma flow on resistive tearing modes

Effects of parallel sound wave damping and drift kinetic damping on the resistive wall mode stability with various plasma rotation profiles

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