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  • 1
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    Relativistic Particle-In-Cell Simulations of Particle Accleration in Relativistic Jets (2008)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: Highly accelerated particles are observed in astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), microquasars, and Gamma-Ray Bursts (GRBs). Particle-In-Cell (PIC) simulations of relativistic electron-ion and electron-positron jets injected into a stationary medium show that efficient acceleration occurs downstream in the jet. In collisionless relativistic shocks particle acceleration is due to plasma waves and their associated instabilities, e.g., the Buneman instability, other two-stream instabilities, and the Weibel (filamentation) instability. Simulations show that the Weibel instability is responsible for generating and amplifying highly non-uniform, small-scale magnetic fields. The instability depends on strength and direction of the magnetic field. Particles in relativistic jets may be accelerated in a complicated dynamics of relativistic jets with magnetic field. We present results of our recent PIC simulations.
    Keywords: Astrophysics
    Type: 37th COSPAR Scientific Assembly; Jul 13, 2008 - Jul 20, 2008; Montreal; Canada
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  • 2
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    New Relativistic Particle-In-Cell Simulation Studies of Prompt and Early Afterglows from GRBs (2008)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations of relativistic electron-ion (electro-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In the collisionless relativistic shock particle acceleration is due to plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel (filamentation) instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The 'jitter' radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.
    Keywords: Astrophysics
    Type: 37th COSPAR Scientific Assembly; Jul 13, 2008 - Jul 20, 2008; Montreal; Canada
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  • 3
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    Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields (2009)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Plasma instabilities (e.g., Buneman, Weibel and other two-stream instabilities) excited in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a new 3-D relativistic particle-in-cell code, we have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. The simulation has been performed using a long simulation system in order to study the nonlinear stages of the Weibel instability, the particle acceleration mechanism, and the shock structure. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic (HD) like shock structure. In the leading shock, electron density increases by a factor of 〈_ 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. We discuss the possible implication of our simulation results within the AGN and GRB context. We have calculated the time evolution of the spectrum from two electrons propagating in a uniform parallel magnetic field to verify the technique. The same technique will be used to calculate radiation from accelerated electrons (positrons) in turbulent magnetic fields generated by Weibel instability.
    Keywords: Nuclear Physics
    Type: M09-0458 , M09-0459 , 4th International Conference on Numerical Modeling of Space Plasma Flows (ASTRONUM 2009); Jun 29, 2009 - Jul 03, 2009; Chamonix; France
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  • 4
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    Simulation of Relativistic Shocks and Associated Self-Consistent Radiation (2010)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: Plasma instabilities excited in collisionless shocks are responsible for particle acceleration. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electrons transverse deflection behind the shock. We calculate the radiation from deflected electrons in the turbulent magnetic fields. The properties of this radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants.
    Keywords: Space Radiation
    Type: M10-0176 , M10-0132 , M10-0133 , Dynamical Processes in Space Plasmas; May 11, 2008 - May 19, 2008; Ein-bokek; Israel|High Energy Astrophysics Division (HEAD) 2010; Mar 01, 2010 - Mar 04, 2010; Big Island, HI; United States|Acceleration and Emission Processes at High Energies and their Application to AGN; Jan 25, 2010 - Jan 26, 2010; Paris; France
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  • 5
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    Simulation of Relativistic Shocks and Associated Radiation from Turbulent Magnetic Fields (2009)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: Plasma instabilities excited in collisionless shocks are responsible for particle acceleration. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electron's transverse deflection behind the shock. The jitter'' radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation, which is calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants. New spectra based on simulations will be presented.
    Keywords: Nuclear Physics
    Type: M10-0111 , M10-0175 , High Energy Phenomena in Relativistic Outflows II; Oct 26, 2009 - Oct 30, 2009; Buenes Aires; South Africa|4th International Conference on Numerical Modeling of Space Plasma Flow; Jun 29, 2009 - Jul 03, 2009; Chamonix; France
    Format: text
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