Physics and Phenomenology of Weakly Magnetized, Relativistic Astrophysical Shock Waves

Weakly magnetized, relativistic collisionless shock waves are not only the natural offsprings of relativistic jets in high-energy astrophysical sources, they are also associated with some of the most outstanding displays of energy dissipation through particle acceleration and radiation. Perhaps their most peculiar and exciting feature is that the magnetized turbulence that sustains the acceleration process, and (possibly) the secondary radiation itself, is self-excited by the accelerated particles themselves, so that the phenomenology of these shock waves hinges strongly on the microphysics of the shock. In this review, we draw a status report of this microphysics, benchmarking analytical arguments with particle-in-cell simulations, and extract consequences of direct interest to the phenomenology, regarding, in particular, the so-called microphysical parameters used in phenomenological studies.

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High-resolution sampling of beam-driven plasma wakefields

Nature Communications ◽

10.1038/s41467-020-19811-9 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

S. Schröder ◽

C. A. Lindstrøm ◽

S. Bohlen ◽

G. Boyle ◽

R. D’Arcy ◽

...

Keyword(s):

Electric Fields ◽

High Energy ◽

Acceleration Process ◽

Plasma Parameters ◽

Particle Beams ◽

Particle In Cell ◽

Precise Control ◽

Plasma Wakefield Accelerators ◽

Plasma Wakefield ◽

Good Agreement

AbstractPlasma-wakefield accelerators driven by intense particle beams promise to significantly reduce the size of future high-energy facilities. Such applications require particle beams with a well-controlled energy spectrum, which necessitates detailed tailoring of the plasma wakefield. Precise measurements of the effective wakefield structure are therefore essential for optimising the acceleration process. Here we propose and demonstrate such a measurement technique that enables femtosecond-level (15 fs) sampling of longitudinal electric fields of order gigavolts-per-meter (0.8 GV m−1). This method—based on energy collimation of the incoming bunch—made it possible to investigate the effect of beam and plasma parameters on the beam-loaded longitudinally integrated plasma wakefield, showing good agreement with particle-in-cell simulations. These results open the door to high-quality operation of future plasma accelerators through precise control of the acceleration process.

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Particle acceleration at colliding shock waves

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa799 ◽

2020 ◽

Vol 494 (3) ◽

pp. 3166-3176 ◽

Cited By ~ 2

Author(s):

T Vieu ◽

S Gabici ◽

V Tatischeff

Keyword(s):

Shock Waves ◽

High Energy ◽

Time Dependent ◽

Shock Acceleration ◽

Diffusive Shock Acceleration ◽

Mathematical Methods ◽

Accretion Flows ◽

Self Similar Solution ◽

Self Similar ◽

Accelerated Particles

ABSTRACT We model the diffusive shock acceleration of particles in a system of two colliding shock waves and present a method to solve the time-dependent problem analytically in the test-particle approximation and high energy limit. In particular, we show that in this limit the problem can be analysed with the help of a self-similar solution. While a number of recent works predict hard (E−1) spectra for the accelerated particles in the stationary limit, or the appearance of spectral breaks, we found instead that the spectrum of accelerated particles in a time-dependent collision follows quite closely the canonical E−2 prediction of diffusive shock acceleration at a single shock, except at the highest energy, where a hardening appears, originating a bumpy feature just before the exponential cut-off. We also investigated the effect of the reacceleration of pre-existing cosmic rays by a system of two shocks, and found that under certain conditions spectral features can appear in the cut-off region. Finally, the mathematical methods presented here are very general and could be easily applied to a variety of astrophysical situations, including for instance standing shocks in accretion flows, diverging shocks, backward collisions of a slow shock by a faster shock, and wind–wind or shock–wind collisions.

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Laser-driven acceleration of heavy ions at ultra-relativistic laser intensity

Laser and Particle Beams ◽

10.1017/s0263034618000563 ◽

2018 ◽

Vol 36 (4) ◽

pp. 507-512 ◽

Cited By ~ 1

Author(s):

J. Domański ◽

J. Badziak ◽

M. Marchwiany

Keyword(s):

Laser Pulse ◽

Heavy Ions ◽

Ion Beam ◽

Heavy Ion ◽

High Energy ◽

Target Thickness ◽

High Energy Density ◽

Ion Acceleration ◽

Acceleration Process ◽

Particle In Cell

AbstractThis paper presents the results of numerical investigations into the acceleration of heavy ions by a multi-PW laser pulse of ultra-relativistic intensity, to be available with the Extreme Light Infrastructure lasers currently being built in Europe. In the numerical simulations, performed with the use of a multi-dimensional (2D3V) particle-in-cell code, the thorium target with a thickness of 50 or 200 nm was irradiated by a circularly polarized 20 fs laser pulse with an energy of ~150 J and an intensity of 1023 W/cm2. It was found that the detailed run of the ion acceleration process depends on the target thickness, though in both considered cases the radiation pressure acceleration (RPA) stage of ion acceleration is followed by a sheath acceleration stage, with a significant role in the post-RPA stage being played by the ballistic movement of ions. This hybrid acceleration mechanism leads to the production of an ultra-short (sub-picosecond) multi-GeV ion beam with a wide energy spectrum and an extremely high intensity (>1021 W/cm2) and ion fluence (>1017 cm−2). Heavy ion beams of such extreme parameters are hardly achievable in conventional RF-driven ion accelerators, so they could open the avenues to new areas of research in nuclear and high energy density physics, and possibly in other scientific domains.

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Nonlinear collisionless damping of Weibel turbulence in relativistic blast waves

Journal of Plasma Physics ◽

10.1017/s0022377814000920 ◽

2014 ◽

Vol 81 (1) ◽

Cited By ~ 17

Author(s):

Martin Lemoine

Keyword(s):

Shock Waves ◽

Gamma Ray ◽

Scattering Length ◽

High Energy ◽

Blast Waves ◽

Point Of View ◽

Small Scale ◽

Magnetic Fluctuations ◽

Collisionless Shock ◽

Radiative Processes

The Weibel/filamentation instability is known to play a key role in the physics of weakly magnetized collisionless shock waves. From the point of view of high energy astrophysics, this instability also plays a crucial role because its development in the shock precursor populates the downstream with a small-scale magneto-static turbulence which shapes the acceleration and radiative processes of suprathermal particles. The present work discusses the physics of the dissipation of this Weibel-generated turbulence downstream of relativistic collisionless shock waves. It calculates explicitly the first-order nonlinear terms associated to the diffusive nature of the particle trajectories. These corrections are found to systematically increase the damping rate, assuming that the scattering length remains larger than the coherence length of the magnetic fluctuations. The relevance of such corrections is discussed in a broader astrophysical perspective, in particular regarding the physics of the external relativistic shock wave of a gamma-ray burst.

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Particle-in-Cell Simulations of Astrophysical Relativistic Jets

Universe ◽

10.3390/universe7110450 ◽

2021 ◽

Vol 7 (11) ◽

pp. 450

Author(s):

Athina Meli ◽

Ken-ichi Nishikawa

Keyword(s):

Active Galactic Nuclei ◽

Gamma Ray ◽

Galactic Nuclei ◽

High Energy ◽

Relativistic Jets ◽

High Energy Astrophysics ◽

Jet Interaction ◽

Particle In Cell ◽

Electron Positron ◽

Kinetic Instabilities

Astrophysical relativistic jets in active galactic nuclei, gamma-ray bursts, and pulsars is the main key subject of study in the field of high-energy astrophysics, especially regarding the jet interaction with the interstellar or intergalactic environment. In this work, we review studies of particle-in-cell simulations of relativistic electron–proton (e−−p+) and electron–positron (e±) jets, and we compare simulations that we have conducted with the relativistic 3D TRISTAN-MPI code for unmagnetized and magnetized jets. We focus on how the magnetic fields affect the evolution of relativistic jets of different compositions, how the jets interact with the ambient media, how the kinetic instabilities such as the Weibel instability, the kinetic Kelvin–Helmholtz instability and the mushroom instability develop, and we discuss possible particle acceleration mechanisms at reconnection sites.

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Diagnosing particle acceleration in relativistic jets

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315002100 ◽

2014 ◽

Vol 10 (S313) ◽

pp. 153-158

Author(s):

Markus Böttcher ◽

Matthew G. Baring ◽

Edison P. Liang ◽

Errol J. Summerlin ◽

Wen Fu ◽

...

Keyword(s):

Magnetic Field ◽

Particle Acceleration ◽

Lorentz Factor ◽

High Energy ◽

Shock Acceleration ◽

Relativistic Jets ◽

Diffusive Shock Acceleration ◽

Magnetic Field Generation ◽

Particle Distributions ◽

Particle In Cell

AbstractThe high-energy emission from blazars and other relativistic jet sources indicates that electrons are accelerated to ultra-relativistic (GeV - TeV) energies in these systems. This paper summarizes recent results from numerical studies of two fundamentally different particle acceleration mechanisms potentially at work in relativistic jets: Magnetic-field generation and relativistic particle acceleration in relativistic shear layers, which are likely to be present in relativistic jets, is studied via Particle-in-Cell (PIC) simulations. Diffusive shock acceleration at relativistic shocks is investigated using Monte-Carlo simulations. The resulting magnetic-field configurations and thermal + non-thermal particle distributions are then used to predict multi-wavelength radiative (synchrotron + Compton) signatures of both acceleration scenarios. In particular, we address how anisotropic shear-layer acceleration may be able to circumvent the well-known Lorentz-factor crisis, and how the self-consistent evaluation of thermal + non-thermal particle populations in diffusive shock acceleration simulations provides tests of the bulk Comptonization model for the Big Blue Bump observed in the SEDs of several blazars.

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Reply [ to “Comment on “Increase of ion kinetic temperature across a collisionless shock: I. A new concept by L. C. Lee et al.” and “Ion acceleration in quasiperpendicular magnetosonic shock waves with subcritical Mach number by Y. Ohsawa and J. Sakai””]

Geophysical Research Letters ◽

10.1029/gl013i006p00565 ◽

1986 ◽

Vol 13 (6) ◽

pp. 565-566

Author(s):

Y. Ohsawa

Keyword(s):

Mach Number ◽

Shock Waves ◽

Ion Acceleration ◽

Kinetic Temperature ◽

Collisionless Shock

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PIC methods in astrophysics: simulations of relativistic jets and kinetic physics in astrophysical systems

Living Reviews in Computational Astrophysics ◽

10.1007/s41115-021-00012-0 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Kenichi Nishikawa ◽

Ioana Duţan ◽

Christoph Köhn ◽

Yosuke Mizuno

Keyword(s):

Plasma Physics ◽

Magnetic Reconnection ◽

Laser Plasma ◽

High Performance ◽

Relativistic Jets ◽

Astrophysical Plasmas ◽

Computing Power ◽

Particle In Cell ◽

The Future ◽

Pic Method

AbstractThe Particle-In-Cell (PIC) method has been developed by Oscar Buneman, Charles Birdsall, Roger W. Hockney, and John Dawson in the 1950s and, with the advances of computing power, has been further developed for several fields such as astrophysical, magnetospheric as well as solar plasmas and recently also for atmospheric and laser-plasma physics. Currently more than 15 semi-public PIC codes are available which we discuss in this review. Its applications have grown extensively with increasing computing power available on high performance computing facilities around the world. These systems allow the study of various topics of astrophysical plasmas, such as magnetic reconnection, pulsars and black hole magnetosphere, non-relativistic and relativistic shocks, relativistic jets, and laser-plasma physics. We review a plethora of astrophysical phenomena such as relativistic jets, instabilities, magnetic reconnection, pulsars, as well as PIC simulations of laser-plasma physics (until 2021) emphasizing the physics involved in the simulations. Finally, we give an outlook of the future simulations of jets associated to neutron stars, black holes and their merging and discuss the future of PIC simulations in the light of petascale and exascale computing.

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