Excitation of Flow-Stabilized Resistive Wall Mode by Coupling with Stable Eigenmodes in Tokamaks

Aiba, N.; Hirota, Mitsutomo

doi:10.1103/physrevlett.114.065001

Cited by 2 publications

(1 citation statement)

References 26 publications

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“…This simplified calculation based on reduced MHD includes parallel dynamics but neglects the divergence of the E × B drift ∇ • v ⊥ and the perpendicular resistivity η ⊥ . The purpose of this derivation is threefold: (1) to show that these two last effects are not necessary to obtain the qualitative results, i.e. complex roots and stabilization for positive constantψ matching parameter ∆ ; (2) to illustrate this simple approach for use in other tearing regimes; and (3) to exploit the simplicity of this model to elucidate the physics.…”

Section: Introductionmentioning

confidence: 99%

Real frequency tearing layers with parallel dynamics and the effect on error field locking and resistive wall modes

2019

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Tearing modes with real frequencies in the plasma frame (i.e. in addition to the Doppler shift due to E×B rotation) are of potential importance because of their effect on the locking process. In particular, it has recently been shown [9] that the Maxwell torque on the plasma in the presence of an applied error field is modified significantly for tearing modes having real frequencies near marginal stability. In addition, it is known [10] that resistive wall tearing modes can be destabilized below their nowall limits by rotation, if the tearing modes have real frequencies near marginal stability. In this paper we first derive the tearing mode dispersion relation with pressure gradient, field line curvature and parallel dynamics in the resistive-inertial (RI) regime, neglecting the divergence of the E ×B drift and perpendicular resistivity. The results show that the usual Glasser effect, a toroidal effect which involves real frequencies, occurs in this simplified model, which ignores perpendicular resistivity and the divergence of the E × B drift. We also find, using a similar simple model, the surprising result that in the viscoresistive regime with pressure gradient, favorable curvature due to toroidal effects, and parallel dynamics, a similar Glasser-like effect is found. We show that in both regimes the existence of tearing modes with complex frequencies is related to nearby electrostatic resistive interchange modes with complex frequencies. We discuss the effect on locking to an error field and the significant lowering of the threshold for destabilization of resistive wall tearing modes, which can be much more pronounced than the weak effect observed for RI tearing modes without pressure-curvature drive in Ref. [10].

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Section: Introductionmentioning

confidence: 99%

Real frequency tearing layers with parallel dynamics and the effect on error field locking and resistive wall modes

2019

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Magnetohydrodynamic instability excited by interplay between a resistive wall mode and stable ideal magnetohydrodynamic modes in rotating tokamak plasmas

Aiba

Hirota

2015

Physics of Plasmas

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In a rotating toroidal plasma surrounded by a resistive wall, it is shown that linear magnetohydrodynamic (MHD) instabilities can be excited by interplay between the resistive wall mode (RWM) and stable ideal MHD modes, where the RWM can couple with not only a stable external kink mode but also various stable Alfvén eigenmodes that abound in a toroidal plasma. The RWM growth rate is shown to peak repeatedly as the rotation frequency reaches specific values for which the frequencies of the ideal MHD modes are Doppler-shifted to the small RWM frequency. Such destabilization can be observed even when the RWM in a static plasma is stable. A dispersion relation clarifies that the unstable mode changes from the RWM to the ideal MHD mode destabilized by wall resistivity when the rotation frequency passes through these specific values. The unstable mode is excited at these rotation frequencies even though plasma rotation also tends to stabilize the RWM from the combination of the continuum damping and the ion Landau damping.

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Excitation of Flow-Stabilized Resistive Wall Mode by Coupling with Stable Eigenmodes in Tokamaks

Cited by 2 publications

References 26 publications

Real frequency tearing layers with parallel dynamics and the effect on error field locking and resistive wall modes

Real frequency tearing layers with parallel dynamics and the effect on error field locking and resistive wall modes

Magnetohydrodynamic instability excited by interplay between a resistive wall mode and stable ideal magnetohydrodynamic modes in rotating tokamak plasmas

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