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1/39 New Relativistic Particle-In-Cell Simulation Studies of Prompt and Early Afterglows from GRBs Ken Nishikawa National Space Science & Technology Center/CSPAR (UAH) Collaborators: P. Hardee (Univ. of Alabama, Tuscaloosa) Y. Mizuno (Univ. Nevada, Las Vegas/CSPAR) M. Medvedev (Univ. of Kansas) B. Zhang (Univ. Nevada, Las Vegas) Å. Nordlund (Neils Bohr Institute) J. Frederiksen (Neils Bohr Institute) J. Niemiec (Institute of Nuclear Physics PAN) Y. Lyubarsky (Ben-Gurion University) H. Sol (Meudon Observatory) D. H. Hartmann (Clemson Univ.) G. J. Fishman (NASA/MSFC ) KINETIC MODELING OF ASTROPHYSICAL PLASMA S, October 7, 2008 2/39 Outline of talk • Recent 3-D particle simulations of relativistic jets * e±pair jet into e±pair and electron-ion ambient plasmas = 12.57, 1 < <30 (avr ≈ 12.6) • Radiation from two electrons • One example of jitter radiation in turbulent magnetic field created by the Weibel instability • Summary • Future plans of our simulations of relativistic jets Calculation of radiation based on particle trajectories 3/39 Schematic GRB from a massive stellar progenitor (Meszaros, Science 2001) Simulation box Prompt emission Polarization ? Accelerated particles emit waves at shocks 4/39 3-D simulation with MPI code injected at z = 25Δ X Y 105×105×4005 grids (not scaled) 1.2 billion particles Z jet front 3-D isosurfaces of density of jet particles and Jz for narrow jet (γv||=12.57) electron-ion ambient t = 59.8ωe-1 electron-positron ambient jet electrons (blue), positrons (gray) -Jz (red), magnetic field lines (white) 6/39 Isosurfaces of z-component of current density for narrow jet (γv = 12.57) || electron-ion ambient plasma electron-positron ambient plasma (+Jz: blue, -Jz:red) local magnetic field lines (white curves) 3-D isosurfaces of z-component of current Jz for narrow jet (γv||=12.57) electron-ion ambient t = 59.8ωe-1 -Jz (red), +Jz (blue), magnetic field lines (white) Particle acceleration due to the local reconnections during merging current filaments at the nonlinear stage thin filaments merged filaments Ion Weibel instability 8/39 ion current E B acceleration electron trajectory (Hededal et al 2004) t = 59.8ωe-1 9/39 Magnetic field generation and particle acceleration with narrow jet (u|| = γv|| = 12.57) B electron-positron ambient εBmax = 0.012 jet electrons electron-ion ambient εBmax = 0.061 jet electrons ambient positrons ambient ions red dot: jet electrons blue dots: ambient (positrons and ions) (Ramirez-Ruiz, Nishikawa, Hededal 2007) 10/39 New simulation results using new MPI_Tristan γ = 15.02, nj/nb = 0.676 t = 1500ωpe−1 electron-positron jet x/Δ = 400 11/39 New simulation results using new MPI_Tristan γ = 15.02, nj/nb = 0.676 t = 1950ωpe−1 x/Δ = 400 12/39 Present theory of Synchrotron radiation (Nakar’s talk on Monday) • Fermi acceleration (Monte Carlo simulations are not selfconsistent; particles are crossing at the shock surface many times and accelerated, the strength of turbulent magnetic fields are assumed), New simulations show Fermi acceleration (Spitkovsky 2008) • The strength of magnetic fields is assumed based on the equipartition (magnetic field is similar to the thermal energy) (B) • The density of accelerated electrons are assumed by the power low (F() = p; p = 2.2?) (e) • Synchrotron emission is calculated based on p and B • There are many assumptions in this calculation 13/39 Self-consistent calculation of radiation • Electrons are accelerated by the electromagnetic field generated by the Weibel instability (without the assumption used in test-particle simulations for Fermi acceleration) • Radiation is calculated by the particle trajectory in the self-consistent magnetic field • This calculation include Jitter radiation (Medvedev 2000, 2006) which is different from standard synchrotron emission • Some synchrotron radiation from electron is reported (Nishikawa et al. 2008 (astroph/0801.4390;0802.2558) 14/39 Radiation from collisionless shock New approach: Calculate radiation from integrating position, velocity, and acceleration of ensemble of particles (electrons and positrons) Hededal, Thesis 2005 (astroph/0506559)Nishikawa et al. 2008 (astroph/0802.2558) 15/39 Synchrotron radiation from gyrating electrons in a uniform magnetic field electron trajectories B β β n β radiation electric field observed at long distance observer β n spectra with different viewing angles time evolution of three frequencies 0° 4° 3° 2° 1° 6° 5° theoretical synchrotron spectrum f/ωpe = 8.5, 74.8, 654. 16/39 Synchrotron radiation from propagating electrons in a uniform magnetic field electron trajectories B radiation electric field observed at long distance θ observer spectra with different viewing angles gyrating θΓ = 13.5° Nishikawa et al. astro-ph/0809.5067 17/39 (Nishikawa et al. astro-ph/0809.5067) 18/39 Case A (Nishikawa et al. astro-ph/0809.5067) 19/39 Case B (Nishikawa et al. astro-ph/0809.5067) 20/39 Case C (Nishikawa et al. astro-ph/0809.5067) 21/39 Case D (Nishikawa et al. astro-ph/0809.5067) 22/39 Case E (Nishikawa et al. astro-ph/0809.5067) 23/39 Case F (Nishikawa et al. astro-ph/0809.5067) 24/39 Radiation from collisionless shock ☺ Power observer Shock simulations GRB Hededal Thesis: Hededal & Nordlund 2005, submitted to ApJL (astro-ph/0511662) Summary 25/39 • Simulation results show electromagnetic stream instability driven by streaming e± pairs are responsible for the excitation of near-equipartition, turbulent magnetic fields. • Ambient ions assist in generation of stronger magnetic fields. • Weibel instability plays a major role in particle acceleration due the quasi-steady radial electric field around the current filaments and local reconnections during merging filaments in relativistic jets. • Broadband (not monoenergetic) jets sustain the stronger magnetic field over a longer region. • The magnetic fields created by Weibel instability generate highly inhomogeneous magnetic fields, which is responsible for jitter radiation (Medvedev, 2000, 2006; Fleishman 2006). 26/39 Future plans for particle acceleration in relativistic jets • Further simulations with a systematic parameter survey will be performed in order to understand shock dynamics with larger systems • Simulations with magnetic field may accelerate particles further? • In order to investigate shock dynamics further diagnostics will be developed • Investigate synchrotron (jitter) emission, and/or polarity from the accelerated electrons in inhomogeneous magnetic fields and compare with observations (Blazars and gamma-ray burst emissions) (Medvedev, 2000, 2006; Fleishman 2006) 27/39 Gamma-Ray Large Area Space Telescope (GLAST) (launched on June 11, 2008) Compton Gamma-Ray http://www-glast.stanford.edu/ Observatory (CGRO) Burst And Transient Source Experiment (BATSE) (1991-2000) PI: Jerry Fishman GLAST All sky monitor • Large Area Telescope (LAT) PI: Peter Michaelson: gamma-ray energies between 20 MeV to about 300 GeV • GLAST Burst Monitor (GBM) PI: Chip Meegan (MSFC): X-rays and gamma rays with energies between 8 keV and 25 MeV (http://gammaray.nsstc.nasa.gov/gbm/) The combination of the GBM and the LAT provides a powerful tool for studying radiation from relativistic jets and gamma-ray bursts, particularly for timeresolved spectral studies over very large energy band. GRB progenitor 28/39 relativistic jet Fushin (god of wind) emission (shocks, acceleration) Raishin (god of lightning) (Tanyu Kano 1657)