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 Accelerated particles emit waves at shocks Schematic GRB from a massive stellar progenitor (Meszaros, Science 2001) Prompt emission Polarization ? Simulation box

4/39 3-D simulation Z X Y jet front jet 105×105×4005 grids (not scaled) 1.2 billion particles injected at z = 25Δ Weibel inst with MPI code

) 3-D isosurfaces of density of jet particles and J z for narrow jet (γv || =12.57) jet electrons (blue), positrons (gray) electron-positron ambient electron-ion ambient -J z (red), magnetic field lines (white) t = 59.8ω e -1

6/39 Isosurfaces of z-component of current density ) for narrow jet ( γ v || = 12.57) electron-ion ambient plasma electron-positron ambient plasma (+J z : blue, -J z :red) local magnetic field lines (white curves)

) 3-D isosurfaces of z-component of current J z for narrow jet (γv || =12.57) electron-ion ambient -J z (red), +J z (blue), magnetic field lines (white) t = 59.8ω e -1 Particle acceleration due to the local reconnections during merging current filaments at the nonlinear stage thin filamentsmerged filaments

8/39 Ion Weibel instability (Hededal et al 2004) E  B acceleration electron trajectory ion current

t = 59.8ω e -1 9/39 Magnetic field generation and particle acceleration with narrow jet (u || = γv || = 12.57) electron-ion ambient ε Bmax = electron-positron ambient ε Bmax = (Ramirez-Ruiz, Nishikawa, Hededal 2007) red dot: jet electrons blue dots: ambient (positrons and ions) jet electrons ambient positrons ambient ions BB

10/39 New simulation results using new MPI_Tristan γ = 15.02, n j /n b = 0.676t = 1500ω pe −1 x/Δ = 400 electron-positron jet

11/39 New simulation results using new MPI_Tristan γ = 15.02, n j /n b = 0.676t = 1950ω pe −1 x/Δ = 400

12/39 Present theory of Synchrotron radiation Fermi acceleration (Monte Carlo simulations are not self- consistent; 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 (Nakar’s talk on Monday)

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 (astro- ph/ ; )

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 (astro- ph/ )Nishikawa et al (astro- ph/ )

15/39 Synchrotron radiation from gyrating electrons in a uniform magnetic field β β n n  B β  β  electron trajectories radiation electric field observed at long distance spectra with different viewing angles 0° theoretical synchrotron spectrum 1°2°3° 6° time evolution of three frequencies 4° 5° observer f/ω pe = 8.5, 74.8, 654.

16/39 Synchrotron radiation from propagating electrons in a uniform magnetic field electron trajectoriesradiation electric field observed at long distance spectra with different viewing angles observer B gyrating θ θ Γ = 13.5° Nishikawa et al. astro-ph/

17/39 (Nishikawa et al. astro-ph/ )

18/39 (Nishikawa et al. astro-ph/ ) Case A

19/39 (Nishikawa et al. astro-ph/ ) Case B

20/39 (Nishikawa et al. astro-ph/ ) Case C

21/39 (Nishikawa et al. astro-ph/ ) Case D

22/39 (Nishikawa et al. astro-ph/ ) Case E

23/39 (Nishikawa et al. astro-ph/ ) Case F

24/39 Radiation from collisionless shock GRB Shock simulations Hededal Thesis: Hededal & Nordlund 2005, submitted to ApJL (astro-ph/ ) Power ☺ observer

25/39 Summary 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) 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 ( The combination of the GBM and the LAT provides a powerful tool for studying radiation from relativistic jets and gamma-ray bursts, particularly for time- resolved spectral studies over very large energy band. Burst And Transient Source Experiment (BATSE) ( ) PI: Jerry Fishman Compton Gamma-Ray Observatory (CGRO) GLAST All sky monitor

28/39 GRB progenitor emission relativistic jet Fushin Raishin (Tanyu Kano 1657) (shocks, acceleration) (god of wind) (god of lightning)