A microscopic analysis of shear acceleration

Abstract

A microscopic analysis of the viscous energy gain of energetic particles in (gradual) non-relativistic shear flows is presented. We extend previous work and derive the Fokker-Planck coefficients for the average rate of momentum change and dispersion in the general case of a momentum-dependent scattering time $\tau (p)\propto p^{\alpha }$ with $\alpha \ge 0$. We show that in contrast to diffusive shock acceleration the characteristic shear acceleration timescale depends inversely on the particle mean free path which makes the mechanism particularly attractive for high energy seed particles. Based on an analysis of the associated Fokker-Planck equation we show that above the injection momentum $p_0$ power-law differential particle number density spectra $n(p)\propto p^{-(1+\alpha )}$ are generated for $\alpha >0$ if radiative energy losses are negligible. We discuss the modifications introduced by synchrotron losses and determine the contribution of the accelerated particles to the viscosity of the background flow. Possible implications for the plasma composition in mildly relativistic extragalactic jet sources (WATs) are addressed.

16 pages, two figures; accepted for publication in Astrophysical Journal

References in corpus (12)

• Radio to Gamma-Ray Emission from Shell-type Supernova Remnants: Predictions from Non-linear Shock Acceleration Models
• Relativistic models and the jet velocity field in the radio galaxy 3C 31
• Radiation from the Relativistic Jet: a Role of the Shear Boundary Layer
• Shear acceleration in relativistic astrophysical jets
• A Chandra and XMM-Newton study of the wide-angle tail radio galaxy 3C465
• Multifrequency observations of the jets in the radio galaxy NGC 315
• Shock Acceleration of Cosmic Rays - a critical review
• Jet Speeds in Wide Angle Tailed Radio Galaxies
• Coaxial Jets and Sheaths in Wide-Angle-Tail Radio Galaxies
• Particle Acceleration in Gamma-Ray Burst Jets
• A MODEL FOR THE RADIO EMISSION FROM SNR 1987A
• Particle acceleration in astrophysical shear flows

Cited by in corpus (38)

• Protostars: Forges of cosmic rays?
• Fermi acceleration in astrophysical jets
• The Hard VHE Gamma-ray Emission in High-Redshift TeV Blazars: Comptonization of Cosmic Microwave Background Radiation in an Extended Jet?
• An Introduction to Particle Acceleration in Shearing Flows
• Ultrahigh-energy Cosmic-ray Nuclei from Black Hole Jets: Recycling Galactic Cosmic Rays through Shear Acceleration
• Time dependent simulations of multiwavelength variability of the blazar Mrk 421 with a Monte Carlo multi-zone code
• The stellar contribution to the extra-galactic background light and absorption of high-energy gamma-rays
• Generalized Fermi acceleration
• Particle Acceleration in Mildly Relativistic Shearing Flows: the Interplay of Systematic and Stochastic Effects, and the Origin of the Extended High-energy Emission in AGN Jets
• Magnetic Field Generation and Particle Energization at Relativistic Shear Boundaries in Collisionless Electron-Positron Plasmas
• PIC Simulation Methods for Cosmic Radiation and Plasma Instabilities
• Particle Acceleration in Shearing Flows: Efficiencies and Limits
• The spectra of jet bases in FR I radio galaxies: implications for particle acceleration
• Turbulent Shear Acceleration
• Non-thermal emission from cosmic rays accelerated in HII regions
• Multiwavelength Observations of the Gamma-Ray Blazar PKS 0528+134 in Quiescence
• Constraining the shear acceleration model for the X-ray emission of large-scale extragalactic jets
• Scrutinizing FR 0 Radio Galaxies as Ultra-High-Energy Cosmic Ray Source Candidates
• 3C 279 in Outburst in June 2015: A Broadband-SED Study Based on the INTEGRAL Detection
• Particle Diffusion and Acceleration in Magnetorotational Instability Turbulence
• Active Galactic Nuclei as potential Sources of Ultra-High Energy Cosmic Rays
• Active Galactic Nuclei Jets and Multiple Oblique Shock Acceleration: Starved Spectra
• Particle acceleration in shearing flows: the case for large-scale jets
• Shear Acceleration in Expanding Flows
• Novel Analysis of the Multiwavelength Structure of Relativistic Jet in Quasar 3C 273
• Boundary Shear Acceleration in the Jet of MKN501
• Turbulence and Particle Acceleration in Shearing Flows
• Cosmic Ray Acceleration in Hydromagnetic Flux Tubes
• Coupling of Damped and Growing Modes in Unstable Shear Flow
• Strong Magnetization Measured in the Cool Cores of Galaxy Clusters
• Extreme ion acceleration at extragalactic jet termination shocks
• The effect of background flow shear on gyrokinetic turbulence in the cold ion limit
• High energy neutrinos produced in the accretion disks by neutrons from nuclei disintegrated in the AGN jets
• Synthetic Neutrino Imaging of a Microquasar
• Spine-sheath jet model for low-luminosity AGNs
• Simulated Radio and Neutrino Imaging of a Microquasar
• Neutrino Emission from Proton Photon Jet Interactions in Microquasars
• Particle Acceleration in Relativistic Shearing Flows: Energy Spectrum