Particle acceleration, magnetization and radiation in relativistic shocks

Abstract

What are the mechanisms of particle acceleration and radiation, as well as magnetic field build up and decay in relativistic shocks are open questions with important implications to various phenomena in high energy astrophysics. While the Weibel instability is possibly responsible for magnetic field build up and diffusive shock acceleration is a model for acceleration, both have problems and current PIC simulation show that particles are accelerated only under special conditions and the magnetic field decays on a short length scale. We present here a novel model for the structure and the emission of highly relativistic collisionless shocks. The model takes into account (and is based on) non-local energy and momentum transport across the shock front via emission and absorption of high-energy photons. This leads to a pre-acceleration of the fluid and pre-amplificaiton of the magnetic fields in the upstream region. Both have drastic implications on the shock structure. The model explains the persistence of the shock generated magnetic field at large distances from the shock front. The dissipation of this magnetic field results in a continuous particle acceleration within the downstream region. The model suggests two non-uniform emission zones (the downstream and the upstream), that give rise to three emission components with different spectral and temporal properties. A unique feature of the model is the existence of an "attractor", toward which any shock will evolve. This enables us to estimate from first principles the synchrotron and inverse Compton spectrum of the downstream emission. The model is applicable to any relativistic shock, but its distinctive features show up only for large compactness. We demonstrate that prompt and afterglow Gamma-Ray Bursts' shocks satisfy the relevant conditions and compare their observations with the predictions.

MNRAS accepted, largely reworked presentation

References in corpus (11)

• Particle acceleration in relativistic collisionless shocks: Fermi process at last?
• On the structure of relativistic collisionless shocks in electron-ion plasmas
• Relativistic Shocks: Particle Acceleration and Magnetization
• Long Term Evolution of Magnetic Turbulence in Relativistic Collisionless Shocks: Electron-Positron Plasmas
• Towards a Better Understanding of the GRB Phenomenon: a New Model for GRB Prompt Emission and its effects on the New Non-Thermal L${}_{\mathrm{i}}^{\mathrm{NT}}$-E${}_{\mathrm{peak},\mathrm{i}}^{\mathrm{rest},\mathrm{NT}}$ relation
• Nonlinear dynamics of the ion Weibel-filamentation instability: an analytical model for the evolution of the plasma and spectral properties
• Synchrotron emission in the fast cooling regime: which spectra can be explained?
• Radiation from relativistic jets in blazars and the efficient dissipation of their bulk energy via photon breeding
• Non-linear collisionless damping of Weibel turbulence in relativistic blast waves
• Sub-photospheric, radiation mediated shocks in GRBs: Multiple shock emission and the Band spectrum
• Impact of continuous particle injection on generation and decay of the magnetic field in collisionless shocks

Cited by in corpus (16)

• The physical conditions of the afterglow implied by MAGIC's sub-TeV observations of GRB 190114C
• GRB afterglow parameters in the era of TeV observations: the case of GRB~190114C
• Physics and phenomenology of weakly magnetized, relativistic astrophysical shock waves
• Physics of relativistic collisionless shocks: II Dynamics of the background plasma
• A semi-analytic afterglow with thermal electrons and synchrotron self-Compton emission
• Impact of continuous particle injection on generation and decay of the magnetic field in collisionless shocks
• Microphysics of Relativistic Collisionless Electron-ion-positron Shocks
• Plasma kinetic effects in relativistic radiation mediated shocks
• Onset of particle acceleration during the prompt phase in gamma-ray bursts as revealed by synchrotron emission in GRB160821A
• The formation of hard VHE spectra from GRB afterglow via Two-Zone Synchrotron Self-Compton Emission
• Gamma-Ray Burst prompt emission from the synchrotron radiation of relativistic electrons in a rapidly decaying magnetic field
• Radiation-mediated shocks: kinetic processes and transition to collisionless shocks
• Relating quasi-stationary one zone emission models to expanding relativistic shocks
• Properties of magnetic turbulence in GRB afterglows
• Broadband Modelling of GRB 230812B Afterglow: Implications for VHE $\gamma$-ray Detection with IACTs
• Major Change in Understanding of GRBs at TeV