Drift-tearing magnetic islands in tokamak plasmas

Journal Article · Tue Jan 15 00:00:00 EST 2008 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2829757· OSTI ID:21069963

Fitzpatrick, R; Waelbroeck, F L ^[1]

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1. Institute for Fusion Studies, Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

A systematic fluid theory of nonlinear magnetic island dynamics in conventional low-{beta}, large aspect-ratio, circular cross-section tokamak plasmas is developed using an extended magnetohydrodynamics model that incorporates diamagnetic flows, ion gyroviscosity, fast parallel electron heat transport, the ion sound wave, the drift wave, and average magnetic field-line curvature. The model excludes the compressible Alfven wave, geodesic field-line curvature, neoclassical effects, and ion Landau damping. A collisional closure is used for plasma dynamics parallel to the magnetic field. Two distinct branches of island solutions are found, namely the 'sonic' and 'hypersonic' branches. Both branches are investigated analytically, using suitable ordering schemes, and in each case the problem is reduced to a relatively simple set of nonlinear differential equations that can be solved numerically via iteration. The solution determines the island phase velocity, relative to the plasma, and the effect of local currents on the island stability. Sonic islands are relatively wide, flatten both the temperature and density profiles, and tend to propagate close to the local ion fluid velocity. Hypersonic islands, on the other hand, are relatively narrow, only flatten the temperature profile, radiate drift-acoustic waves, and tend to propagate close to the local electron fluid velocity. The hypersonic solution branch ceases to exist above a critical island width. Under normal circumstances, both types of island are stabilized by local ion polarization currents.

• OSTI ID: 21069963
• Journal Information: Physics of Plasmas, Vol. 15, Issue 1; Other Information: DOI: 10.1063/1.2829757; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALFVEN WAVES
ASPECT RATIO
ELECTRIC CURRENTS
ELECTRONS
HEAT TRANSFER
IONS
LANDAU DAMPING
MAGNETIC FIELDS
MAGNETIC ISLANDS
MAGNETOHYDRODYNAMICS
MATHEMATICAL SOLUTIONS
NEOCLASSICAL TRANSPORT THEORY
NONLINEAR PROBLEMS
PHASE VELOCITY
PLASMA
PLASMA DENSITY
PLASMA DRIFT
SOUND WAVES
TOKAMAK DEVICES
WAVE PROPAGATION