The toroidal 1/1 internal kink mode

Journal Article · Sun Aug 01 04:00:00 EDT 1999 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.873568· OSTI ID:355446

Sugiyama, L E ^[1]

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1. Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States)

The m{sup 0}/n=1/1 internal mode in toroidal plasma is shown to have an intrinsic dependence on a (global) epsilon beta-poloidal ({epsilon}{beta}{sub p}) parameter independent of the inverse aspect ratio {epsilon}, when the degree of compressibility is determined self-consistently. The {epsilon}{beta}{sub p} parameter introduces properties very different from those predicted from strict incompressibility, where the mode depends strongly on aspect ratio. An exact solution and scaling properties are presented numerically. A companion paper provides a supporting analysis based on small parameter solutions of the toroidal perturbation equations [L. E. Sugiyama, submitted to Phys. Plasmas (1998)]. The maximal ordering of the mode growth rate is {gamma}=O({epsilon}{sup 1/2}) or ({delta}q){sup 1/2} at low beta, {beta}{sub p}{approximately}1. The compressible mode has two distinct regimes in {epsilon}{beta}{sub p} and {epsilon}=a/R. At moderate {epsilon}{beta}{sub p}{approx_lt}{epsilon}{lt}1, the growth rate varies linearly with {epsilon}{beta}{sub p}{minus}{epsilon}{beta}{sub pc} and is almost independent of {epsilon} when {delta}q=1{minus}q within q{le}1 is small, {delta}q{approximately}{epsilon}. At very small {epsilon}{lt}{epsilon}{beta}{sub p}, corresponding to large {beta}{sub p}{gt}1 and also to {delta}q{gt}{epsilon}, the growth rate varies as {gamma}{proportional_to}{beta}{sub p}{sup 2}. For the 1/1 mode, the small value of {delta}q=1{minus}q within the region q{lt}1, satisfied by almost all tokamaks with q{sub 0}{lt}1, determines a number of basic properties of the toroidal mode. Small {delta}q makes the m=1 component of the magnetic flux order {delta}q, causing the m=2 component of the toroidal current density to be the same order of magnitude as m=1 on the q=1 surface and thereby giving the 1/1 mode a fundamental inboard/outboard asymmetry{emdash}on the outboard side of the torus the separatrix current sheet vanishes. The asymmetry strengthens with resistivity and in the nonlinear phase. {copyright} {ital 1999 American Institute of Physics.}

• OSTI ID: 355446
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 8 Vol. 6; ISSN 1070-664X; ISSN PHPAEN
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BETA RATIO
KINK INSTABILITY
MAGNETOHYDRODYNAMICS
PLASMA CONFINEMENT
TOKAMAK DEVICES
TOROIDAL CONFIGURATION