Two-Dimensional Kelvin-Helmholtz Instability with Anisotropic Pressure

Abstract

The Kelvin-Helmholtz (KH) instability occurs in multiple heliospheric (solar-wind stream interfaces, planetary magnetospheres, cometary tails, heliopause flanks) and interstellar (protoplanetary disks, relativistic jets, neutron star accretion disks) environments. While the KH instability has been well-studied in the magnetohydrodynamic (MHD) limit, only limited studies were performed in the collisionless regime, which is conducive to development of anisotropic pressures. Collisionless plasmas are often described using the Chew Goldberger and Low (CGL) equations which feature an anisotropic pressure tensor. This paper presents a comprehensive analysis of the CGL version of the KH instability using linearised and numerical techniques. We find that the largest growth rates and the greatest incidence of magnetic effects occur in the MHD limit. In the large relaxation time CGL limit, part of the energy goes into the formation of pressure anisotropies, resulting in smaller amounts of energy being available for bending the field lines. Consequently, when we cross-compare CGL and MHD simulations that are otherwise identical, the current densities are largest in the MHD limit, and the largest magnetic islands also form in that limit. Early and late time formation of pressure anisotropies have also been studied. We also find that the strongest trend for forming intermittencies in the flow also occurs in the MHD limit. The paper also discusses possible consequences of our results for turbulence and reconnection in the heliosheath (the layer between the solar wind termination shock and the heliopause).

Accepted In The Astrophysical Journal (In Press)

References in corpus (14)

• Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar wind
• Growth and saturation of the Kelvin-Helmholtz instability with parallel and anti-parallel magnetic fields
• The Magnetohydrodynamic Kelvin-Helmholtz Instability: A Three-Dimensional Study of Nonlinear Evolution
• The MHD Kelvin-Helmholtz Instability II: The Roles of Weak and Oblique Fields in Planar Flows
• The Kelvin-Helmholtz Instability at CME-Boundaries in the Solar Corona: Observations and 2.5D MHD Simulations
• Kelvin-Helmholtz instability in solar chromospheric jets: theory and observation
• Magnetic Field Generation in Core-Sheath Jets via the Kinetic Kelvin-Helmholtz Instability
• Solar Orbiter Observations of the Kelvin-Helmholtz Instability in the Solar Wind
• The MHD Kelvin-Helmholtz Instability III: The Role of Sheared Magnetic Field in Planar Flows
• Numerical Studies of the Kelvin-Hemholtz Instability in the Coronal Jet
• Kelvin-Helmholtz Instability of the Magnetopause of Disc-Accreting Stars
• Going Beyond the MHD Approximation: Physics-Based Numerical Solution of the CGL Equations
• Physical Constraint Preserving Higher Order Finite Volume Schemes for Divergence-Free Astrophysical MHD and RMHD
• An Alternative Finite Difference WENO-like Scheme with Physical Constraint Preservation for Divergence-Preserving Hyperbolic Systems