Magnetohydrodynamic stability and nonlinear evolution of the m = 1 mode in toroidal geometry for safety factor profiles with an inflection point

Journal Article · Fri Mar 31 23:00:00 EST 1989 · Phys Fluids B; (United States)

DOI:https://doi.org/10.1063/1.859003· OSTI ID:6338505

Holmes, J A; Carreras, B A; Charlton, L A

Magnetohydrodynamic (MHD) stability and nonlinear evolution of the m = 1 mode are studied in toroidal geometry for safety factor profiles having an inflection point at the q = 1 surface. For ideally stable cases, linear growth rates of the resistive m = 1 mode are decreased by any combination of the following variations: decreasing the aspect ratio, decreasing shear at the q = 1 surface, increasing S, decreasing q/sub 0/, and/or decreasing beta. Transitions from resistive kink to tearing mode to complete stability are accompanied by increasing localization as the mode is stabilized. The ideal stability of the m = 1 mode for low-shear inflection-point profiles is broken at very low, but finite, beta by the appearance of a radially localized ideal interchange mode. As beta is increased, the m = 1 mode becomes a global ideal internal kink. These ideal modes are stabilized by decreasing the aspect ratio and, to a lesser extent, by increasing shear at the q = 1 surface. Nonlinear evolution of the m = 1 mode is found to follow the Kadomtsev complete reconnection process or to be stable, depending on the linear stability of the mode. However, all nonlinear calculations were carried out at Lundquist number S = 10/sup 5/ and hence contain substantial resistive kink contributions. Consequently, nonlinear evolution in the m = 1 tearing mode regime is not examined. Even for cases in which ideal effects dominate the linear mode, Kadomtsev reconnection is observed. The nonlinear stability of linearly stable modes was also uniformly observed, even for several cases having large initial perturbations.

• Research Organization: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
• OSTI ID: 6338505
• Journal Information: Phys Fluids B; (United States), Journal Name: Phys Fluids B; (United States) Vol. 1:4; ISSN PFBPE
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107* -- Fusion Energy-- Plasma Research-- Instabilities
ANNULAR SPACE
ASPECT RATIO
CLOSED CONFIGURATIONS
CLOSED PLASMA DEVICES
CONFIGURATION
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
INSTABILITY GROWTH RATES
KINK INSTABILITY
MAGNETIC FIELD CONFIGURATIONS
MAGNETOHYDRODYNAMICS
MECHANICS
NONLINEAR PROBLEMS
PLASMA
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
SPACE
STABILITY
TEARING INSTABILITY
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
TOROIDAL CONFIGURATION