Finite. beta. effects on the nonlinear evolution of the (m = 1; n = 1) mode in tokamaks
The stability and evolution of ISX-B-like plasmas are numerically studied using a reduced set of resistive magnetohydrodynamic equations. For a sequence of equilibria stable to ideal modes, the n = 1 mode changes from a tearing branch to a pressure-driven branch as ..beta../sub p/ is increased. When this mode is unstable at low ..beta.., it is just the (m = 1; n = 1) tearing mode. Higher n modes also become linearly unstable with increasing ..beta../sub p/; they are essentially pressure-driven and have ballooning character. For low values of ..beta.., the instability is best described as a ..beta../sub p/ distortion of the (m = 1; n = 1) tearing mode. This mode drives many other helicities through toroidal and nonlinear couplings. As ..beta../sub p/ is increased, the growth of the m = 1 island slows down in time, going from exponential to linear before reconnection occurs. If ..beta../sub p/ is large enough, the island saturates without reconnection. A broad spectrum of other modes, driven by the (m = 1; n = 1) instability, is produced. These results agree with some observed features of magnetohydrodynamic activity in ISX-B.
- Research Organization:
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5522992
- Journal Information:
- Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 25:5; ISSN PFLDA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
700107* -- Fusion Energy-- Plasma Research-- Instabilities
700108 -- Fusion Energy-- Plasma Research-- Wave Phenomena
BETA RATIO
FLUID MECHANICS
HYDRODYNAMICS
ISX TOKAMAK
MAGNETOHYDRODYNAMICS
MECHANICS
NONLINEAR PROBLEMS
NUMERICAL SOLUTION
OSCILLATION MODES
PLASMA
STABILITY
THERMONUCLEAR REACTORS
TOKAMAK TYPE REACTORS