Double tearing instability with shear flow

Journal Article · Tue Sep 01 04:00:00 EDT 1992 · Physics of Fluids B; (United States)

DOI:https://doi.org/10.1063/1.860148· OSTI ID:7153343

Ofman, L ^[1]

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

The linear evolution of the double tearing mode with parallel to the magnetic field equilibrium shear flow and viscosity is investigated numerically. Numerically obtained growth rates are found to agree with the solutions of the double tearing dispersion relation in the parameter range of validity. Solutions of the incompressible, time-dependent, linearized, viscoresistive magnetohydrodynamic equations for the double tearing mode with parallel flow are found for wide relevant parameter ranges. Large (weakly coupled) and small (strongly coupled) rational surface separation {ital y}{sub {ital s}} are investigated. The magnetic Reynolds number {ital S} is varied up to 10{sup 8}, and ambient flow velocities up to 0.57 of the Alfven speed {ital V}{sub A} far from the tearing layer are considered. The normalized wave number {alpha} is 0.05 (long wavelength) and 0.5 (short wavelength). Spatial variations of the perturbed magnetic field {psi} and flow {ital W} indicate the nonconstant-{psi}'' effects for small {ital y}{sub {ital s}}. Shear flow decouples the rational surfaces, reduces the growth rate, and transforms the instability to the standard tearing mode. Overstable modes are found from the solutions of the dispersion relation and in the numerical computations, and their frequencies are not affected by the value of viscosity. The temporal oscillations of the solutions increase with the flow at the resonant surfaces at a rate slower than that of the Doppler shift. For viscous Reynolds number {ital S}{sub {ital v}} comparable to or larger than the magnetic Reynolds number a stabilizing effect was found, and in the presence of large flow the real growth rate {gamma}{sub {ital R}} scaling approaches the standard tearing mode scaling {gamma}{sub {ital R}}{similar to}{ital S}{sub {ital v}}{sup 1/6}.

• DOE Contract Number: FG05-80ET53088
• OSTI ID: 7153343
• Journal Information: Physics of Fluids B; (United States), Journal Name: Physics of Fluids B; (United States) Vol. 4:9; ISSN 0899-8221; ISSN PFBPE
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700340* -- Plasma Waves
Oscillations
& Instabilities-- (1992-)
700370 -- Plasma Fluid & MHD Properties-- (1992-)
DISPERSION RELATIONS
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
INSTABILITY GROWTH RATES
MAGNETOHYDRODYNAMICS
MECHANICS
NUMERICAL SOLUTION
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
REYNOLDS NUMBER
SCALING
TEARING INSTABILITY
VISCOSITY