scholarly journals Diagnosing particle acceleration in relativistic jets

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.

scholarly journals 3-D RPIC simulations of relativistic jets: Particle acceleration, magnetic field generation, and emission

2007 ◽  
Author(s):  
Ken-Ichi Nishikawa ◽  
P. E. Hardee ◽  
C. B. Hededal ◽  
Yosuke Mizuno ◽  
G. J. Fishman
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Relativistic Jets ◽  
Magnetic Field Generation ◽  
Field Generation

scholarly journals Particle Acceleration in Gamma-Ray Bursts

2005 ◽  
Vol 192 ◽  
pp. 475-482
Author(s):  
J.G. Kirk
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Shock Front ◽  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Magnetic Field Generation ◽  
Relativistic Shocks ◽  
The Crab Nebula

SummarySimple kinematic theories of particle acceleration at relativistic shocks lead to the prediction of a high-energy spectral index of −1.1 for the energy flux of synchrotron photons. However, several effects can change this picture. In this paper I discuss the effect of magnetic field generation at the shock front and, by analogy with the Crab Nebula, suggest that an intrinsic break in the injection spectrum should be expected where the electron gyro radius is comparable to that of protons thermalized by the shock.

scholarly journals A Shock-in-Jet Synchrotron Mirror Model for Blazars

Physics ◽  
2021 ◽  
Vol 3 (4) ◽  
pp. 1112-1122
Author(s):  
Markus Böttcher
Keyword(s):  
Synchrotron Radiation ◽  
Gamma Ray ◽  
Low Frequency ◽  
High Energy ◽  
Shock Acceleration ◽  
Additional Parameter ◽  
Diffusive Shock Acceleration ◽  
Spectral Variability ◽  
Particle Distributions ◽  
Self Consistent

Reinhard Schlickeiser has made groundbreaking contributions to various aspects of blazar physics, including diffusive shock acceleration, the theory of synchrotron radiation, the production of gamma-rays through Compton scattering in various astrophysical sources, etc. This paper, describing the development of a self-consistent shock-in-jet model for blazars with a synchrotron mirror feature, is therefore an appropriate contribution to a Special Issue in honor of Reinhard Schlickeiser’s 70th birthday. The model is based on our previous development of a self-consistent shock-in-jet model with relativistic thermal and non-thermal particle distributions evaluated via Monte-Carlo simulations of diffusive shock acceleration, and time-dependent radiative transport. This model has been very successful in modeling spectral variability patterns of several blazars, but has difficulties describing orphan flares, i.e., high-energy flares without a significant counterpart in the low-frequency (synchrotron) radiation component. As a solution, this paper investigates the possibility of a synchrotron mirror component within the shock-in-jet model. It is demonstrated that orphan flares result naturally in this scenario. The model’s applicability to a recently observed orphan gamma-ray flare in the blazar 3C279 is discussed and it is found that only orphan flares with mild (≲ a factor of 2–3) enhancements of the Compton dominance can be reproduced in a synchrotron-mirror scenario, if no additional parameter changes are invoked.

3-D Rpic Simulations of Relativistic Jets: Particle Acceleration, Magnetic Field Generation, and Emission

2006 ◽  
Vol 307 (1-3) ◽  
pp. 319-323 ◽  
Author(s):  
K.-I. Nishikawa ◽  
C. B. Hededal ◽  
P. E. Hardee ◽  
G. J. Fishman ◽  
C. Kouveliotou ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Relativistic Jets ◽  
Magnetic Field Generation ◽  
Field Generation

3-D RPIC Simulations of Relativistic Jets: Particle Acceleration, Magnetic Field Generation, and Emission

2007 ◽  
pp. 319-323
Author(s):  
K. -I. Nishikawa ◽  
C. B. Hededal ◽  
P. E. Hardee ◽  
G. J. Fishman ◽  
C. Kouveliotou ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Relativistic Jets ◽  
Magnetic Field Generation ◽  
Field Generation

scholarly journals An Introduction to Particle Acceleration in Shearing Flows

Galaxies ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 78 ◽  
Author(s):  
Frank Rieger
Keyword(s):  
Particle Acceleration ◽  
Large Scale ◽  
Shear Flows ◽  
Charged Particles ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
Astrophysical Plasmas ◽  
Particle Distributions ◽  
Recent Developments ◽  
Type Particle

Shear flows are ubiquitously present in space and astrophysical plasmas. This paper highlights the central idea of the non-thermal acceleration of charged particles in shearing flows and reviews some of the recent developments. Topics include the acceleration of charged particles by microscopic instabilities in collisionless relativistic shear flows, Fermi-type particle acceleration in macroscopic, gradual and non-gradual shear flows, as well as shear particle acceleration by large-scale velocity turbulence. When put in the context of jetted astrophysical sources such as Active Galactic Nuclei, the results illustrate a variety of means beyond conventional diffusive shock acceleration by which power-law like particle distributions might be generated. This suggests that relativistic shear flows can account for efficient in-situ acceleration of energetic electrons and be of relevance for the production of extreme cosmic rays.

scholarly journals Acceleration of Charged Particles in Astrophysical Plasmas

2021 ◽  
Vol 8 ◽  
Author(s):  
Siming Liu ◽  
J. Randy Jokipii
Keyword(s):  
Particle Acceleration ◽  
Magnetic Fields ◽  
Electric Fields ◽  
Charged Particles ◽  
High Energy ◽  
Shock Acceleration ◽  
High Energy Particle ◽  
Acceleration Of Particles ◽  
Diffusive Shock Acceleration ◽  
Astrophysical Plasmas

The origin of high-energy particles in the Universe is one of the key issues of high-energy solar physics, space science, astrophysics, and particle astrophysics. Charged particles in astrophysical plasmas can be accelerated to very high energies by electric fields. Based on the characteristics of interactions between charged particles and electric fields carried by the background plasma, the mechanisms of charged particle acceleration can be divided into several groups: resonant interactions between plasma waves and particles, acceleration by electric fields parallel to magnetic fields, and acceleration caused by drift of the guiding center of particle gyro-motion around magnetic fields in magnetic field in-homogeneity-related curvature and gradient, etc. According to macroscopic energy conversion mechanisms leading to acceleration of particles, several theories of particle acceleration have been developed: stochastic particle acceleration by turbulent electromagnetic fields, diffusive shock acceleration of particles, and particle acceleration during magnetic re-connections. These theories have their own assumptions and characteristics and find applications in different astrophysical contexts. With advances in high-energy astrophysical observations and in combination with analyses of characteristics of high-energy particle acceleration and radiation, we can better understand the underlying physical processes in dramatically evolving astrophysical environments.

scholarly journals MULTIWAVELENGTH PROBES OF THE ENVIRONS OF RELATIVISTIC SHOCKS IN BLAZAR JETS

2014 ◽  
Vol 28 ◽  
pp. 1460167 ◽  
Author(s):  
MATTHEW G. BARING ◽  
MARKUS BÖTTCHER ◽  
ERROL J. SUMMERLIN
Keyword(s):  
Gamma Ray ◽  
Mean Free Path ◽  
High Energy ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
Particle Distributions ◽  
Astrophysical Jet ◽  
Relativistic Shocks ◽  
Diagnostic Potential ◽  
Power Law Index

Diffusive shock acceleration (DSA) at relativistic shocks is likely to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud AGN. An important recent development for blazar science is the ability of Fermi-LAT data to pin down the power-law index of the high energy portion of emission in these sources, and therefore also the index of the underlying non-thermal particle population. This diagnostic potential was not possible prior to Fermi launch, when gamma-ray information was dominated by the highly-absorbed TeV band. This paper highlights how multiwavelength spectra including X-ray band and Fermi data can be used to probe diffusive acceleration in relativistic, oblique, MHD shocks in blazar jets. The spectral index of the non-thermal particle distributions resulting from Monte Carlo simulations of DSA, and the fraction of thermal particles accelerated to non-thermal energies, depend sensitively on the particles' mean free path scale, and also on the magnetic field obliquity to the shock normal. We investigate self-consistently the radiative synchrotron/Compton signatures of the resulting thermal and non-thermal particle distributions. Important constraints on the frequency of particle scattering and the level of field turbulence are identified for the blazar AO 0235+164. The possible interpretation that turbulence levels decline with remoteness from jet shocks, and a significant role for non-gyroresonant diffusion, are discussed.

scholarly journals The formation of relativistic plasma structures and their potential role in the generation of cosmic ray electrons

2008 ◽  
Vol 15 (6) ◽  
pp. 831-846 ◽  
Author(s):  
M. E. Dieckmann
Keyword(s):  
Magnetic Field ◽  
Phase Space ◽  
Magnetic Energy ◽  
Ion Beam ◽  
Cosmic Ray ◽  
Compact Objects ◽  
Space Structures ◽  
Magnetic Field Generation ◽  
Particle In Cell ◽  
Field Generation

Abstract. Recent particle-in-cell (PIC) simulation studies have addressed particle acceleration and magnetic field generation in relativistic astrophysical flows by plasma phase space structures. We discuss the astrophysical environments such as the jets of compact objects, and we give an overview of the global PIC simulations of shocks. These reveal several types of phase space structures, which are relevant for the energy dissipation. These structures are typically coupled in shocks, but we choose to consider them here in an isolated form. Three structures are reviewed. (1) Simulations of interpenetrating or colliding plasma clouds can trigger filamentation instabilities, while simulations of thermally anisotropic plasmas observe the Weibel instability. Both transform a spatially uniform plasma into current filaments. These filament structures cause the growth of the magnetic fields. (2) The development of a modified two-stream instability is discussed. It saturates first by the formation of electron phase space holes. The relativistic electron clouds modulate the ion beam and a secondary, spatially localized electrostatic instability grows, which saturates by forming a relativistic ion phase space hole. It accelerates electrons to ultra-relativistic speeds. (3) A simulation is also revised, in which two clouds of an electron-ion plasma collide at the speed 0.9c. The inequal densities of both clouds and a magnetic field that is oblique to the collision velocity vector result in waves with a mixed electrostatic and electromagnetic polarity. The waves give rise to growing corkscrew distributions in the electrons and ions that establish an equipartition between the electron, the ion and the magnetic energy. The filament-, phase space hole- and corkscrew structures are discussed with respect to electron acceleration and magnetic field generation.

scholarly journals Detection of TeV Gamma Rays from SN1006

1998 ◽  
Vol 188 ◽  
pp. 121-124 ◽  
Author(s):  
Toru Tanimori
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Gamma Rays ◽  
High Energy ◽  
Shock Acceleration ◽  
Emission Region ◽  
X Ray ◽  
High Energy Electrons ◽  
Tev Gamma Rays ◽  
The Magnetic Field

In spite of the recent progress of high energy gamma-ray astronomy, there still remains quite unclear and important problem about the origin of cosmic rays. Supernova remnants (SNRs) are the favoured site for cosmic rays up to 1016 eV, as they satisfy the requirements such as an energy input rate. But direct supporting evidence is sparse. Recently intense non-thermal X-ray emission from the rims of the Type Ia SNR SN1006 (G327.6+14.6) has been observed by ASCA (Koyama et al. 1995)and ROSAT (Willingale et al. 1996), which is considered, by attributing the emission to synchrotron radiation, to be strong evidence of shock acceleration of high energy electrons up to ~100 TeV. If so, TeV gamma rays would also be expected from inverse Compton scattering (IC) of low energy photons (mostly attributable to the 2.7 K cosmic background photons) by these electrons. By assuming the magnetic field strength (B) in the emission region of the SNR, several theorists (Pohl 1996; Mastichiadis 1996; Mastichiadis & de Jager 1996; Yoshida & Yanagita 1997) calculated the expected spectra of TeV gamma rays using the observed radio/X-ray spectra. Observation of TeV gamma rays would thus provide not only the further direct evidence of the existence of very high energy electrons but also the another important information such as the strength of the magnetic field and diffusion coefficient of the shock acceleration. With this motivation, SN1006 was observed by the CANGAROO imaging air Cerenkov telescope in 1996 March and June, also 1997 March and April.

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