The MHD Kelvin-Helmholtz Instability III: The Role of Sheared Magnetic Field in Planar Flows

Abstract

We have carried out simulations of the nonlinear evolution of the magnetohydrodynamic (MHD) Kelvin-Helmholtz (KH) instability for compressible fluids in $2\frac{1}{2}$-dimensions, extending our previous work by Frank et al (1996) and Jones \etal (1997). In the present work we have simulated flows in the x-y plane in which a ``sheared'' magnetic field of uniform strength ``smoothly'' rotates across a thin velocity shear layer from the z direction to the x direction, aligned with the flow field. We focus on dynamical evolution of fluid features, kinetic energy dissipation, and mixing of the fluid between the two layers, considering their dependence on magnetic field strength for this geometry. The introduction of magnetic shear can allow a Cat's Eye-like vortex to form, even when the field is stronger than the nominal linear instability limit given above. For strong fields that vortex is asymmetric with respect to the preliminary shear layer, however, so the subsequent dissipation is enhanced over the uniform field cases of comparable field strength. In fact, so long as the magnetic field achieves some level of dynamical importance during an eddy turnover time, the asymmetries introduced through the magnetic shear will increase flow complexity, and, with that, dissipation and mixing. The degree of the fluid mixing between the two layers is strongly influenced by the magnetic field strength. Mixing of the fluid is most effective when the vortex is disrupted by magnetic tension during transient reconnection, through local chaotic behavior that follows.

14 pages including 9 figures (4 figures in degraded jpg format), full paper with original quality figures available via anonymous ftp at ftp://canopus.chungnam.ac.kr/ryu/mhdkh2d.uu, to appear in The Astrophysical Journal

References in corpus (1)

• Enhanced Cloud Disruption by Magnetic Field Interaction

Cited by in corpus (13)

• The Magnetohydrodynamic Kelvin-Helmholtz Instability: A Three-Dimensional Study of Nonlinear Evolution
• Numerical Study of Turbulent Mixing Layers with Non-Equilibrium Ionization Calculations
• High order ADER schemes for a unified first order hyperbolic formulation of Newtonian continuum mechanics coupled with electro-dynamics
• Local simulations of the magnetized Kelvin-Helmholtz instability in neutron-star mergers
• The two-dimensional magnetohydrodynamic Kelvin-Helmholtz instability: compressibility and large-scale coalescence effects
• Quantifying energetics and dissipation in magnetohydrodynamic turbulence
• Numerical simulations of Kelvin-Helmholtz instability: a two-dimensional parametric study
• Numerical Studies of the Kelvin-Hemholtz Instability in the Coronal Jet
• 3D simulations of shear instabilities in magnetized flows
• The Kelvin-Helmholtz instability in weakly ionised plasmas II: multifluid effects in molecular clouds
• The impact of magnetic fields on momentum transport and saturation of shear-flow instability by stable modes
• Magnetized Kelvin-Helmholtz instability in the presence of a radiation field
• Two-Dimensional Kelvin-Helmholtz Instability with Anisotropic Pressure