Relativistic Plasma Research Articles

Polarized Anisotropic Synchrotron Emission and Absorption and Its Application to Black Hole Imaging

Low-collisionality plasma in a magnetic field generically develops anisotropy in its distribution function with respect to the magnetic field direction. Motivated by the application to radiation from accretion flows and jets, we explore the effect of temperature anisotropy on synchrotron emission. We derive analytically and provide numerical fits for the polarized synchrotron emission and absorption coefficients for a relativistic bi-Maxwellian plasma (we do not consider Faraday conversion/rotation). Temperature anisotropy can significantly change how the synchrotron emission and absorption coefficients depend on observing angle with respect to the magnetic field. The emitted linear polarization fraction does not depend strongly on anisotropy, while the emitted circular polarization does. We apply our results to black hole imaging of Sgr A* and M87* by ray tracing a GRMHD simulation and assuming that the plasma temperature anisotropy is set by the thresholds of kinetic-scale anisotropy-driven instabilities. We find that the azimuthal asymmetry of the 230 GHz images can change by up to a factor of 3, accentuating (T ⊥ > T ∥) or counteracting (T ⊥ < T ∥) the image asymmetry produced by Doppler beaming. This can change the physical inferences from observations relative to models with an isotropic distribution function, e.g., by allowing for larger inclination between the line of sight and spin direction in Sgr A*. The observed image diameter and the size of the black hole shadow can also vary significantly due to plasma temperature anisotropy. We describe how the anisotropy of the plasma can affect future multifrequency and photon ring observations. We also calculate kinetic anisotropy-driven instabilities (mirror, whistler, and firehose) for relativistically hot plasmas.

Effect of incoherence in a heavy nucleus nonlinear wave in a degenerate relativistic magneto-rotating quantum plasma

Effect of incoherence in a heavy nucleus nonlinear wave in a degenerate relativistic magneto-rotating quantum plasma

Relaxation of relativistic pair plasma in a massive photon field

The relaxation of relativistic hot electron–positron plasma is investigated by incorporating the effect of non-zero photon mass, and a quadruple Beltrami (QB) relaxed state for the magnetic vector potential is derived. The QB state is a linear superposition of four single force-free fields and is characterized by four self-organized structures of different length scales. The analysis of QB states shows that for certain values of generalized helicities at lower relativistic temperatures, plasma shows diamagnetic behaviour. It is also noteworthy that the inclusion of non-zero photon mass naturally provides the possibility of multiscale structure formation in the relaxed state. In this scenario, one of the field structures is significantly larger than the Compton wavelength of photons, while the other three structures are on the scale of the electron skin depth. The potential implications of this QB state for astrophysical environments are also discussed.

Parametric study of the polarization dependence of nonlinear Breit–Wheeler pair creation process using two laser pulses

With the rapid development of high-power petawatt class lasers worldwide, exploring physics in the strong field QED regime will become one of the frontiers for laser–plasma interactions research. Particle-in-cell codes, including quantum emission processes, are powerful tools for predicting and analyzing future experiments where the physics of relativistic plasma is strongly affected by strong field QED processes. The spin/polarization dependence of these quantum processes has been of recent interest. In this article, we perform a parametric study of the interaction of two laser pulses with an ultrarelativistic electron beam. The first pulse is optimized to generate high-energy photons by nonlinear Compton scattering and efficiently decelerate electron beam through the quantum radiation reaction. The second pulse is optimized to generate electron–positron pairs by the nonlinear Breit–Wheeler decay of photons with the maximum polarization dependence. This may be experimentally realized as a verification of the strong field QED framework, including the spin/polarization rates.

Study of a Highly Magnetized Relativistic Plasma in the Context of Laboratory Astrophysics and Particle Flow Control

Study of a Highly Magnetized Relativistic Plasma in the Context of Laboratory Astrophysics and Particle Flow Control

Electron-Acoustic Waves and Parametric Instabilities in 3-Component Relativistic Quantum Plasma with a Beam of Non-relativistic Quantum Electrons

Electron-Acoustic Waves and Parametric Instabilities in 3-Component Relativistic Quantum Plasma with a Beam of Non-relativistic Quantum Electrons

Kinetic theory for spin-polarized relativistic plasmas

The investigation of spin and polarization effects in ultra-high intensity laser–plasma and laser–beam interactions has become an emergent topic in high-field science recently. In this paper, we derive a relativistic kinetic description of spin-polarized plasmas, where quantum-electrodynamics effects are taken into account via Boltzmann-type collision operators under the local constant field approximation. The emergence of anomalous precession is derived from one-loop self-energy contributions in a strong background field. We are interested, in particular, in the interplay between radiation reaction effects and the spin polarization of the radiating particles. For this, we derive equations for spin-polarized quantum radiation reaction from moments of the spin-polarized kinetic equations. By comparing with the classical theory, we identify and discuss the spin-dependent radiation reaction terms and radiative contributions to spin dynamics.

Formation and Evolution of Transient Jets and Their Cavities in Black Hole X-Ray Binaries

We propose a model explaining the origin of transient/episodic jets in black hole X-ray binaries, in which they are caused by transitions from a collimated, strongly magnetized jet to a wide, uncollimated outflow. The change occurs when the accretion flow leaves the magnetically choked state due to an increase of the accretion rate for a weakly varying magnetic flux. The formed powerful jet then detaches from its base, and propagates as a discrete ejection. The uncollimated outflow then produces a relativistic plasma that fills the surroundings of the black hole, contributing to the formation of a low-density cavity. While the pressure in the cavity is in equilibrium with the surrounding interstellar medium (ISM), its inertia is orders of magnitude lower than that of the ISM. This implies that the plasma cannot efficiently decelerate the ejecta, explaining most of the observations. The modest deceleration within the cavities observed in some cases can then be due to the presence of clouds and/or filaments, forming a wide transition zone between the cavity and the ISM.

Impact of temperature asymmetry and small fraction of static positive ions on the relaxed states of a relativistic hot pair plasma

Abstract The relaxed state of a magnetized relativistic hot plasma composed of inertial electrons and positrons having different relativistic temperatures and a fraction of static positive ions is studied. From the steady-state solutions of vortex dynamics equations and the relation for current density, a non-force-free triple Beltrami (TB) relaxed state equation is derived. The TB state is characterized by three scale parameters that consequently provide three different self-organized structures. The analysis of the relaxed state shows that for specific values of generalized helicities, the disparity in relativistic temperature and the existence of a small fraction of static positive ions in pair plasma can transform the nature of scale parameters. Moreover, an analytical solution of the TB state for an axisymmetric cylindrical geometry with an internal conductor configuration demonstrates that due to asymmetries of temperature and density of plasma species, diamagnetic structures can transform into paramagnetic ones and vice versa. The present study will improve our understanding of pair plasmas in trap-based plasma confinement experiments and astrophysical environments.

Transverse expansion of Bjorken flow in (1+1D) relativistic ideal-magnetohydrodynamics with magnetization

We study the evolution of magnetized quark gluon plasma (QGP) in the magneto hydrodynamic (MHD) framework. The fluid under investigation has a non-zero magnetization with infinite electrical conductivity. We solve the coupled Maxwell and conservation equations in (1+1D) transverse flow. We assume that the motion of fluid is longitudinally boost-invariant along beam line.In this study, we consider two different scenarios. First, we consider an ideal relativistic plasma with massless particles and infinite electrical conductivity with a constant magnetic susceptibility (χm). Thus, we solve the coupled Maxwell and conservation equations, and obtain the transverse fluid velocity, the energy density and the magnetic field as functions of both space and time. We investigate the effects of magnetic susceptibility (χm) on the evolution of thermodynamic quantities. Then, we solve the coupled Maxwell and conservation equations with a temperature-dependent magnetic susceptibility and a realistic equation of state given by lattice-QCD data [43,44]. We find the evaluation of temperature, energy density, the magnetic field, and the transverse fluid velocity. We improve our previous study [21] to include a nonzero magnetization, the transverse relativistic velocity ux2≠0, and a realistic equation of state.We realize the effects of non-zero magnetization on the fluid quantities are rather small. Besides, our work shows a fluid with a realistic equation and a temperature-dependent magnetic susceptibility behaves like a conformal fluid with a small constant magnetic susceptibility.

Propagation of a fast radio burst through a birefringent relativistic plasma

Propagation of a fast radio burst through a birefringent relativistic plasma

Propagation characteristics of a high-power beam in weakly relativistic-ponderomotive thermal quantum plasma

The present work explores the propagation characteristics of high-power beams in weakly relativistic-ponderomotive thermal quantum plasma. A q-Gaussian laser beam is taken in the present investigation. The quasi-optics equation obtained in the present study is solved through a well-established Wentzel–Kramers–Brillouin approximation and paraxial theory approach for obtaining the second-order differential equation describing the behavior of beam width of the laser beam. Further, a numerical simulation of this second-order differential equation is carried out for determining the behavior of the beam width with dimensionless distance for established laser–plasma parameters. The comparison of the present study is made with ordinary quantum plasma and classical relativistic plasma cases.

Extreme ion acceleration at extragalactic jet termination shocks

Context. Extragalactic plasma jets are some of the few astrophysical environments able to confine ultra-high-energy cosmic rays, but whether they are capable of accelerating these particles is unknown. Aims. In this work, we revisit particle acceleration at relativistic magnetized shocks beyond the local uniform field approximation by considering the global transverse structure of the jet. Methods. Using large two-dimensional particle-in-cell simulations of a relativistic electron-ion plasma jet, we show that the termination shock forming at the interface with the ambient medium accelerates particles up to the confinement limit. Results. The radial structure of the jet magnetic field leads to a relativistic velocity shear that excites a von Kármán vortex street in the downstream medium trailing behind an over-pressured bubble filled with cosmic rays. Particles are efficiently accelerated at each crossing of the shear flow boundary layers. Conclusions. These findings support the idea that extragalactic plasma jets may be capable of producing ultra-high-energy cosmic rays. This extreme particle acceleration mechanism may also apply to microquasar jets.

EZ: An efficient, charge conserving current deposition algorithm for electromagnetic particle-in-cell simulations

We present EZ, a novel current deposition algorithm for particle-in-cell (PIC) simulations. EZ calculates the current density on the electromagnetic grid due to macro-particle motion within a time step by solving the continuity equation of electrodynamics. Being a charge conserving hybridization of Esirkepov's method and ZigZag, we refer to it as “EZ” as shorthand for “Esirkepov meets ZigZag”. Simulations of a warm, relativistic plasma with PIConGPU show that EZ achieves the same level of charge conservation as the commonly used method by Esirkepov, yet reaches higher performance for macro-particle assignment-functions up to third-order. In addition to a detailed description of the functioning of EZ, reasons for the expected and observed performance increase are given, and guidelines for its implementation aiming at highest performance on GPUs are provided.

Effects of two-temperature electrons on the slow and fast modulation instability and envelope solitons in a fully relativistic plasma

Effects of two-temperature electrons on the slow and fast modulation instability and envelope solitons in a fully relativistic plasma

Two-color high-harmonic generation from relativistic plasma mirrors.

High-intensity laser solid interactions are capable of generating attosecond light bursts via high-harmonic generation-most work focuses on single beam interactions. In this paper, we perform a numerical investigation on the role of wavelength and polarization in relativistic, high-harmonic generation from normal-incidence, two-beam interactions off plasma mirrors. We find that the two-beam harmonic-generation mechanism is a robust process described by a set of well-defined selection rules. We demonstrate that the emitted harmonics from normal-incidence interactions exhibit an intensity optimization when the incident fields are of equal intensity for two-color circularly polarized fields.

On the modulational of Schamel nonlinear Schrödinger equation and the associated envelope excitations in a degenerate relativistic quantum complex plasma

The modulational instability (MI) of Schamel/modified nonlinear Schrödinger equation (SNLSE) or (mNLSE) and the associated envelope excitations, including bright solitons in a multicomponent dense plasma consisting of relativistically degenerate electrons, trapped ions, and non-degenerate dust species are reported. A conventional multiple scales perturbative technique is utilized to get a SNLSE. This equation is different from the standard NLSE which the SNLSE has a nonlinear term with fractional order (3/2). The MI criteria are derived in detail. Also, the occurrence of envelope solitary wave and the effects of the different physical parameters on its profile are briefly discussed. The current results are advantageous to understand the mechanism of the propagation of the envelope excitations in complex plasmas with trapped ions and relativistically degenerate electrons, such as those observed in space observations and laboratory complex plasma.

Mechanism of vorticity amplification by elastic waves in a viscoelastic channel flow

Inertia-less viscoelastic channel flow displays a supercritical nonnormal mode elastic instability due to finite-size perturbations despite its linear stability. The nonnormal mode instability is determined mainly by a direct transition from laminar to chaotic flow, in contrast to normal mode bifurcation leading to a single fastest-growing mode. At higher velocities, transitions to elastic turbulence and further drag reduction flow regimes occur accompanied by elastic waves in three flow regimes. Here, we demonstrate experimentally that the elastic waves play a key role in amplifying wall-normal vorticity fluctuations by pumping energy, withdrawn from the mean flow, into wall-normal fluctuating vortices. Indeed, the flow resistance and rotational part of the wall-normal vorticity fluctuations depend linearly on the elastic wave energy in three chaotic flow regimes. The higher (lower) the elastic wave intensity, the larger (smaller) the flow resistance and rotational vorticity fluctuations. This mechanism was suggested earlier to explain elastically driven Kelvin-Helmholtz-like instability in viscoelastic channel flow. The suggested physical mechanism of vorticity amplification by the elastic waves above the elastic instability onset recalls the Landau damping in magnetized relativistic plasma. The latter occurs due to the resonant interaction of electromagnetic waves with fast electrons in the relativistic plasma when the electron velocity approaches light speed. Moreover, the suggested mechanism could be generally relevant to flows exhibiting both transverse waves and vortices, such as Alfven waves interacting with vortices in turbulent magnetized plasma, and Tollmien-Schlichting waves amplifying vorticity in both Newtonian and elasto-inertial fluids in shear flows.

Nonlinear coupling of electromagnetic and spin-electron-acoustic waves in spin-polarized degenerate relativistic astrophysical plasma

Propagation of the finite amplitude electromagnetic wave through the partially spin-polarized degenerate plasmas leads to an instability. This instability happens due to the interaction of the electromagnetic wave with the small-frequency longitudinal spin-electron-acoustic waves. The strongest growth of the instability happens in the high-density degenerate plasmas with the Fermi momentum close to mec, where me is the mass of electron and c is the speed of light. The increase of the instability increment with the growth of the spin polarization of plasmas is found.

Effect of relativistic ponderomotive force on shock waves in a relativistic degenerate plasma

Abstract We investigate the effect of relativistic ponderomotive force on the propagation of shock waves in relativistic degenerate plasma, which is relevant to high-intensity laser-plasma experiments aimed at replicating extreme conditions on white dwarfs. We derive the KdV-Burger’s equation by incorporating the density modification induced by the ponderomotive force and hence demonstrate that this equation is a suitable model for shock waves affected by ponderomotive force. Unlike previous studies that use ponderomotive force as a source of nonlinearity to derive the nonlinear Schrödinger equation for envelope solitons, our study focuses on the effect of ponderomotive force on shocks produced by the intense laser. We show that the ponderomotive force can significantly modify the strength and shape of shock waves, providing insight into the underlying physics of shock waves in relativistic degenerate plasmas which may help to better understand experimental observations in this regime.