Relativistic Turbulence with Strong Synchrotron and Synchrotron-Self-Compton Cooling

Abstract

Many relativistic plasma environments in high-energy astrophysics, including pulsar wind nebulae, hot accretion flows onto black holes, relativistic jets in active galactic nuclei and gamma-ray bursts, and giant radio lobes, are naturally turbulent. The plasma in these environments is often so hot that synchrotron and inverse-Compton (IC) radiative cooling becomes important. In this paper we investigate the general thermodynamic and radiative properties (and hence the observational appearance) of an optically thin relativistically hot plasma stirred by driven magnetohydrodynamic (MHD) turbulence and cooled by radiation. We find that if the system reaches a statistical equilibrium where turbulent heating is balanced by radiative cooling, the effective electron temperature tends to attain a universal value $\theta =k{T}_e/m_e{c}^2\sim 1/\sqrt{{\tau }_T}$, where ${\tau }_T=n_e{\sigma }_{T}L\ll 1$ is the system's Thomson optical depth, essentially independent of the strength of turbulent driving or magnetic field. This is because both MHD turbulent dissipation and synchrotron cooling are proportional to the magnetic energy density. We also find that synchrotron self-Compton (SSC) cooling and perhaps a few higher-order IC components are automatically comparable to synchrotron in this regime. The overall broadband radiation spectrum then consists of several distinct components (synchrotron, SSC, etc.), well separated in photon energy (by a factor $\sim {\tau }_T^{-1}$) and roughly equal in power. The number of IC peaks is checked by Klein-Nishina effects and depends logarithmically on ${\tau }_T$ and the magnetic field. We also examine the limitations due to synchrotron self-absorption, explore applications to Crab PWN and blazar jets, and discuss links to radiative magnetic reconnection.

12 pages, 1 figure; replaced with a slightly modified revised version matching the final published (in MNRAS) article

References in corpus (14)

• Observations of the Crab Nebula with H.E.S.S
• Fast TeV variability in blazars: jets in a jet
• Kinetic Simulations of Magnetized Turbulence in Astrophysical Plasmas
• Turbulent Structure of a Stratified Supernova-Driven Interstellar Medium
• Density Fluctuations in MHD Turbulence: Spectra, Intermittency and Topology
• Implications of very rapid TeV variability in blazars
• Non-thermal particle acceleration in collisionless relativistic electron-proton reconnection
• Rapid variability in TeV blazars: the case of PKS 2155-304
• Pulsar Wind Nebulae as Cosmic Pevatrons: A Current Sheet's Tale
• Kinetic turbulence in relativistic plasma: from thermal bath to non-thermal continuum
• Radiative magnetic reconnection near accreting black holes
• Reconnection in Marginally Collisionless Accretion Disk Coronae
• Spectral and Intermittency Properties of Relativistic Turbulence
• Saturation of the MRI in Strongly Radiation Dominated Accretion Disks

Cited by in corpus (11)

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• Kinetic turbulence in shining pair plasma: intermittent beaming and thermalization by radiative cooling
• Radiative Particle-in-Cell Simulations of Turbulent Comptonization in Magnetized Black-Hole Coronae
• From young to old: the evolutionary path of Pulsar Wind Nebulae
• Sub-photospheric turbulence as a heating mechanism in gamma-ray bursts
• Radiative turbulent flares in magnetically-dominated plasmas
• Balancing Turbulent Heating with Radiative Cooling in Blazars
• Turbulence, Gravity, and Multimessenger Asteroseismology
• Spectral Diversities of Gamma-ray Bursts in High Energy Bands: Hints from Turbulent Cascade
• Heating of Magnetically Dominated Plasma by Alfvén-Wave Turbulence
• Anisotropy and energy distribution of leptons and photons in radiative relativistic Alfvénic turbulence