Evolution of Unmagnetized and Magnetized Shear Layers

Abstract

We present numerical simulations of the growth and saturation of the Kelvin-Helmholtz instability in a compressible fluid layer with and without a weak magnetic field. In the absence of a magnetic field, the instability generates a single eddy which flattens the velocity profile, stabilizing it against further perturbations. Adding a weak magnetic field - weak in the sense that it has almost no effect on the linear instability - leads to a complex flow morphology driven by MHD forces and to enhanced broadening of the layer, due to Maxwell stresses. We corroborate earlier studies which showed that magnetic fields destroy the large scale eddy structure through periodic cycles of windup and resistive decay, but we show that the rate of decay decreases with decreasing plasma resistivity, at least within the range of resistivity accessible to our simulations. Magnetization increases the efficiency of momentum transport, and the transport increases with decreasing resistivity.

17 pages, 14 figures, to be published in ApJ April 20, 2008, v677n2

References in corpus (7)

• Interstellar Turbulence I: Observations and Processes
• Interstellar Turbulence II: Implications and Effects
• The Birth of Molecular Clouds: Formation of Atomic Precursors in Colliding Flows
• Growth and saturation of the Kelvin-Helmholtz instability with parallel and anti-parallel magnetic fields
• The MHD Kelvin-Helmholtz Instability: A Two-Dimensional Numerical Study
• Turbulent Ambipolar Diffusion: Numerical Studies in 2D
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• The Kelvin-Helmholtz instability in weakly ionised plasmas II: multifluid effects in molecular clouds
• Interactions between magnetohydrodynamic shear instabilities and convective flows in the solar interior
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• Advanced numerical methods in astrophysical fluid dynamics