SYNTHETIC SPECTRA FROM PARTICLE-IN-CELL SIMULATIONS OF RELATIVISTIC COLLISIONLESS SHOCKS

Journal Article · Thu Dec 10 04:00:00 UTC 2009 · Astrophysical Journal (Online)

DOI:https://doi.org/10.1088/0004-637X/707/1/L92· OSTI ID:21389312

Sironi, Lorenzo; Spitkovsky, Anatoly ^[1]

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1. Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544-1001 (United States)

We extract synthetic photon spectra from first-principles particle-in-cell simulations of relativistic shocks propagating in unmagnetized pair plasmas. The two basic ingredients for the radiation, namely accelerated particles and magnetic fields, are produced self-consistently as part of the shock evolution. We use the method of Hededal and Nordlund and compute the photon spectrum via Fourier transform of the electric far field from a large number of particles, sampled directly from the simulation. We find that the spectrum from relativistic collisionless shocks is entirely consistent with synchrotron radiation in the magnetic fields generated by Weibel instability. We can recover the so-called 'jitter' regime only if we artificially reduce the strength of the electromagnetic fields, such that the wiggler parameter K ident to qBlambda/mc {sup 2} becomes much smaller than unity (B and lambda are the strength and scale of the magnetic turbulence, respectively). These findings may place constraints on the origin of non-thermal emission in astrophysics, especially for the interpretation of the hard (harder than synchrotron) low-frequency spectrum of gamma-ray bursts.

• OSTI ID: 21389312
• Journal Information: Astrophysical Journal (Online), Journal Name: Astrophysical Journal (Online) Journal Issue: 1 Vol. 707; ISSN 1538-4357
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
ASTROPHYSICS
BOSONS
BREMSSTRAHLUNG
COSMIC GAMMA BURSTS
COSMIC RADIATION
ELECTROMAGNETIC FIELDS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EMISSION
ENERGY RANGE
FOURIER TRANSFORMATION
INTEGRAL TRANSFORMATIONS
IONIZING RADIATIONS
MAGNETIC FIELDS
MASSLESS PARTICLES
PHOTONS
PHYSICS
PLASMA
PRIMARY COSMIC RADIATION
RADIATIONS
RELATIVISTIC RANGE
SIMULATION
SYNCHROTRON RADIATION
THERMAL SHOCK
TRANSFORMATIONS
TURBULENCE