Role of the Kelvin-Helmholtz instability in the evolution of magnetized relativistic sheared plasma flows

Hamlin, Nathaniel; Newman, William I.

doi:10.1103/physreve.87.043101

Cited by 31 publications

(32 citation statements)

References 63 publications

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“…It is important to note that the MI (and the ESKHI) can operate in cold, i.e., highly supersonic shearing flows, where the (magneto)hydrodynamic KHI is suppressed [23,24]. Such shear configurations are stable to macroscopic perturbations and will only trigger microscopic instabilities.…”

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confidence: 99%

Transverse electron-scale instability in relativistic shear flows

et al. 2015

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Electron-scale surface waves are shown to be unstable in the transverse plane of a sheared flow in an initially unmagnetized collisionless plasma, not captured by (magneto)hydrodynamics. It is found that these unstable modes have a higher growth rate than the closely related electron-scale Kelvin-Helmholtz instability in relativistic shears. Multidimensional particle-in-cell simulations verify the analytic results and further reveal the emergence of mushroomlike electron density structures in the nonlinear phase of the instability, similar to those observed in the Rayleigh Taylor instability despite the great disparity in scales and different underlying physics. This transverse electron-scale instability may play an important role in relativistic and supersonic sheared flow scenarios, which are stable at the (magneto)hydrodynamic level. Macroscopic ( c/ω pe ) fields are shown to be generated by this microscopic shear instability, which are relevant for particle acceleration, radiation emission, and to seed magnetohydrodynamic processes at long time scales. A fundamental question in plasma physics concerns the stability of a given plasma configuration. Unstable plasma configurations are ubiquitous and constitute important dissipation sites via the operation of plasma instabilities, which typically convert plasma kinetic energy into thermal and electric or magnetic field energy. Plasma instabilities can occur at microscopic (particle kinetic) and macroscopic [magnetohydrodynamic (MHD)] scales, and are generally studied separately using simplified frameworks that focus on a particular scale and neglect the other. This approach conceals the role that microscopic processes may have on the macroscopic plasma dynamics, which in many scenarios cannot be disregarded. It is now recognized, for instance, that collisionless plasma instabilities operating on the electron scale in unmagnetized plasmas, such as the Weibel [1] and streaming instabilities [2], play a crucial role in the formation of (macroscopic) collisionless shocks in astrophysical [3][4][5][6][7] and laboratory conditions [8,9]. These microscopic instabilities result from the bulk interpenetration between plasmas and are believed to be intimately connected to important questions such as particle acceleration and radiation emission in astrophysical scenarios [10,11].Sheared plasma flow configurations can host both microscopic and macroscopic instabilities simultaneously, although the former have been largely overlooked. Sheared flow settings have been traditionally studied using the MHD framework [12][13][14], where the Kelvin-Helmholtz instability (KHI) is the only instability known to develop [15]. Only very recently have collisionless unmagnetized sheared plasma flows been addressed experimentally [16] and using particle-in-cell (PIC) simulations, revealing a rich variety of electron-scale processes, such as the electron-scale KHI (ESKHI), dc magnetic field generation, and unstable transverse dynamics [17][18][19][20][21][22]. The generated fields and modif...

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confidence: 99%

Transverse electron-scale instability in relativistic shear flows

et al. 2015

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“…We will show that this iterative scheme converges geometrically and that acceleration methods render quadratic the speed of convergence. In typical simulations [16], we have employed the algorithm that we detail below without failure literally many billions of times.…”

Section: Computational Background and Technical Challengesmentioning

confidence: 99%

“…For moderate situations, we will consider one of the many cases presented by Hamlin and Newman [16] for two-dimensional MHD flow with Lorentz factors of around 2. We employed the algorithm detailed here in all those cases but also performed comparison checks using several existing algorithms, including the algorithm developed by Mignone and McKinney [28].…”

Section: Convergence Properties Of the Iterationmentioning

confidence: 99%

“…We have compared our method to those described in section 2 for the moderately relativistic case discussed in section 6, namely, the two-dimensional nonlinear RMHD simulation of the Kelvin-Helmholtz instability from Hamlin and Newman [16]. These are the 5 × 5 method used by Balsara [3], the 3 × 3 method used by Komissarov [24], the method of Del Zanna, Bucciantini, and Londrillo [10], and the method of Mignone and McKinney [28].…”

Section: Computementioning

confidence: 99%

“…In section 5, we present our iterative method for recovering primitive variables. In section 6, we discuss the convergence properties of our method, including its performance in the moderately relativistic RMHD simulations from Hamlin and Newman [16] and then in the highly relativistic cases presented in Komissarov [24]. In section 7, we discuss our use of the Aitken accelerant to render the convergence of our scheme quadratic, which makes quadratic the speed of convergence.…”

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Primitive Variable Determination in Conservative Relativistic Magnetohydrodynamic Simulations

Newman¹,

Hamlin²

2014

SIAM J. Sci. Comput.

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Abstract. In nonrelativistic hydrodynamics and magnetohydrodynamics, conservative integration schemes for the fluid equations of motion are generally employed. The computed quantities, namely, the mass density, (vector) momentum density, and energy density, can readily be converted back into the primitive variables that define the problem, namely, the mass density, (vector) velocity, and thermal pressure. In practical terms, the primitive variables can be "peeled away" from the computed variables. In relativistic problems, however, the appearance of the Lorentz factor in the computed quantities dramatically complicates the problem owing to its near-singular dependence upon relativistic velocities. Conservative integration schemes for the hyperbolic partial differential equations of special relativistic magnetohydrodynamics (RMHD) yield estimates of the five conserved quantities that are related in a highly nonlinear way to the five primitive variables. We also observe that an equivalent set of five nonlinear equations emerges in describing the general relativistic magnetohydrodynamics problem. Conversion from the conserved quantities to primitive variables is the most computationally intensive part of the simulation, consuming almost all the computational effort. This paper presents a new algorithm for accurately and rapidly addressing this problem. We provide an analytic representation for this nonlinear system as a single equation in a single unknown. This equation lends itself to an iterative approach, emerging from its underlying physical and analytic properties, one whose convergence is rapid and sufficiently close to geometric that the Aitken acceleration scheme renders the iterations quadratically convergent. The new algorithm enjoys robust convergence properties that render it well-suited to parallel computing architectures. We show how our new scheme facilitates the rapid and accurate computation of solutions to the RMHD equations for moderate Lorentz factors as well as extreme relativistic situations that are observed in high-energy astrophysical objects, where the Lorentz factor can exceed 10 4 and magnetic fields can exceed 10 13 Gauss, and in laboratory plasmas associated with fusion research where very high velocities and magnetic fields are introduced.

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Nonequilibrium and morphological characterizations of Kelvin–Helmholtz instability in compressible flows

Gan

Zhang

et al. 2019

Front. Phys.

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We investigate the effects of viscosity and heat conduction on the onset and growth of Kelvin-Helmholtz instability (KHI) via an efficient discrete Boltzmann model. Technically, two effective approaches are presented to quantitatively analyze and understand the configurations and kinetic processes. One is to determine the thickness of mixing layers through tracking the distributions and evolutions of the thermodynamic nonequilibrium (TNE) measures; the other is to evaluate the growth rate of KHI from the slopes of morphological functionals. Physically, it is found that the time histories of width of mixing layer, TNE intensity, and boundary length show high correlation and attain their maxima simultaneously. The viscosity effects are twofold, stabilize the KHI, and enhance both the local and global TNE intensities. Contrary to the monotonically inhibiting effects of viscosity, the heat conduction effects firstly refrain then enhance the evolution afterwards. The physical reasons are analyzed and presented.

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Role of the Kelvin-Helmholtz instability in the evolution of magnetized relativistic sheared plasma flows

Cited by 31 publications

References 63 publications

Transverse electron-scale instability in relativistic shear flows

Transverse electron-scale instability in relativistic shear flows

Primitive Variable Determination in Conservative Relativistic Magnetohydrodynamic Simulations

Nonequilibrium and morphological characterizations of Kelvin–Helmholtz instability in compressible flows

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