Low-frequency Alfvén gap modes in rotating tokamak plasmas

Haverkort, J.W.; Blank, HJ de; Koren, Barry

doi:10.1088/0741-3335/53/4/045004

Cited by 5 publications

(18 citation statements)

References 30 publications

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“…It does become very small for marginally stable modes, justifying the use of ω D = 0 in the performed stability analysis. Figure 1(a) also shows two types of modes reported earlier [58]. A Sturmian sequence of modes is present, which have a finite amplitude only in a small range around the rational surface and are polarized within the magnetic surfaces.…”

Section: Simulationssupporting

confidence: 57%

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Stability of localized modes in rotating tokamak plasmas

Haverkort

Blank

2011

Plasma Phys. Control. Fusion

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The ideal magnetohydrodynamic stability is investigated of localized interchange modes in a large-aspect ratio tokamak plasma. The resulting stability criterion includes the effects of toroidal rotation and rotation shear and contains various well-known limiting cases. The analysis allows for a general adiabatic index, resulting in a stabilizing contribution from the convective effect. A further stabilizing effect from rotation exists when the angular frequency squared decreases radially more rapidly than the density. Flow shear, however, also decreases the stabilizing effect of magnetic shear through the KelvinHelmholtz mechanism. Numerical simulations reveal the merits and limitations of the performed local analysis.

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Section: Simulationssupporting

confidence: 57%

“…An analytical rigidly rotating isothermal equilibrium [57,58] is used with γ = 5/3, = 0.1, and β between zero at the plasma edge and a maximum β ≈ 0.015. This resulted in a monotonically increasing q-profile, centred around q 0 = 1 at r 0 ≈ 0.6, where q ≈ 0.023.…”

Section: Simulationsmentioning

confidence: 99%

Stability of localized modes in rotating tokamak plasmas

Haverkort

Blank

2011

Plasma Phys. Control. Fusion

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“…[11]. Similar modes in rotating plasmas have recently [12] been identified numerically using the FINESSE [13] code. In the current paper we present an instructive derivation of finite n GAMs and ZF continua in the presence of toroidal rotation.…”

Section: Introductionmentioning

confidence: 97%

Generalised zonal modes in stationary axisymmetric plasmas

Graves

Wahlberg

2017

Plasma Phys. Control. Fusion

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The MHD model enables derivation and analysis of the rich structure of geodesic acoustic modes (GAMs) and zonal modes in axisymmetric magnetic confined plasmas. The modes are identifiable from a single dispersion relation as two branches of slow magnetosonic continua. The lower frequency branch can be identified as a zonal flow, which in the simplified limit of static plasmas, has vanishing magnetic component. It is shown in this contribution that axisymmetric, and lesser known nonaxisymmetric, zonal modes can be derived from MHD and kinetic models. The work provides a comprehensive derivation of the GAMs and zonal flow continua in static and stationary toroidally rotating plasmas, and investigates the exact solution and structure of a generalised family of zonal modes.

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“…The discrete spectrum of global modes and instabilities arising in these equilibria have been discussed in Refs. [70] and [64], respectively. Here, we will focus on the low-frequency continuous MHD spectrum.…”

Section: Numerical Calculationsmentioning

confidence: 99%

The Brunt–Väisälä frequency of rotating tokamak plasmas

Haverkort

Blank

Koren

2012

Journal of Computational Physics

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a b s t r a c tThe continuous spectrum of analytical toroidally rotating magnetically confined plasma equilibria is investigated analytically and numerically. In the presence of purely toroidal flow, the ideal magnetohydrodynamic equations leave the freedom to specify which thermodynamic quantity is constant on the magnetic surfaces. Introducing a general parametrization of this quantity, analytical equilibrium solutions are derived that still posses this freedom. These equilibria and their spectral properties are shown to be ideally suited for testing numerical equilibrium and stability codes including toroidal rotation. Analytical expressions are derived for the low-frequency continuous Alfvén spectrum. These expressions still allow one to choose which quantity is constant on the magnetic surfaces of the equilibrium, thereby generalizing previous results. The centrifugal convective effect is shown to modify the lowest Alfvén continuum branch to a buoyancy frequency, or Brunt-Väisälä frequency. A comparison with numerical results for the case that the specific entropy, the temperature, or the density is constant on the magnetic surfaces yields excellent agreement, showing the usefulness of the derived expressions for the validation of numerical codes.

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Low-frequency Alfvén gap modes in rotating tokamak plasmas

Cited by 5 publications

References 30 publications

Stability of localized modes in rotating tokamak plasmas

Stability of localized modes in rotating tokamak plasmas

Generalised zonal modes in stationary axisymmetric plasmas

The Brunt–Väisälä frequency of rotating tokamak plasmas

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