Local Kelvin-Helmholtz instability and synchrotron modulation in Pulsar Wind Nebulae

Abstract

We present here a series of numerical simulations of the development of Kelvin-Helmholtz instability in a relativistically hot plasma. The physical parameters in the unperturbed state are chosen to be representative of local conditions encountered in Pulsar Wind Nebulae (PWNe), with a main magnetic field perpendicular to a mildly relativistic shear layers. By using a numerical code for Relativistic MHD, we investigate the effect of an additional magnetic field component aligned with the shear velocity, and we follow the evolution of the instability to the saturation and turbulent regimes. Based on the resulting flow structure, we then compute synchrotron maps in order to evaluate the signature of Kelvin-Helmholtz instability on the emission and we investigate how the time scale and the amplitude of the synchrotron modulations depend on shear velocity and magnetic field. Finally we compare our results to the observed variable features in the Crab Nebula. We show that the Kelvin-Helmholtz instability cannot account for the wisps variability, but it might be responsible for the time dependent filamentary structure observed in the main torus.

10 pages, 7 figures, Accepted for publication in A&A

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• Non-thermal emission from relativistic MHD simulations of PWNe: from synchrotron to inverse Compton
• On the MHD modeling of the Crab Nebula radio emission
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• On the linear theory of Kelvin-Helmholtz instabilities of relativistic magnetohydrodynamic planar flows
• CAFE: A New Relativistic MHD Code
• Implementation of advanced Riemann solvers in a neutrino-radiation magnetohydrodynamics code in numerical relativity and its application to a binary neutron star merger
• The imprint of pulsar parameters on the morphology of Pulsar Wind Nebulae
• The Role of the Equation of State in Resistive Relativistic Magnetohydrodynamics
• Multi-band Emission up to PeV Energy from the Crab Nebula in a Spatially Dependent Lepto-hadronic Model
• The Kelvin-Helmholtz instability in weakly ionised plasmas: Ambipolar dominated and Hall dominated flows
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• MHD models of Pulsar Wind Nebulae
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• Assessing the role of the Kelvin-Helmholtz instability at the QCD cosmological phase transition