RADIATION SIGNATURES OF SUB-LARMOR SCALE MAGNETIC FIELDS

Journal Article · Sat Aug 20 04:00:00 UTC 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/737/2/55· OSTI ID:21579955

Medvedev, Mikhail V ^[1]; Frederiksen, Jacob Trier; Haugboelle, Troels; Nordlund, Ake ^[2]

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1. Institute for Advanced Study, School of Natural Sciences, Princeton, NJ 08540 (United States)
2. Niels Bohr International Academy, Blegdamsvej 17, DK-2199 Koebenhavn Oe (Denmark)

Spontaneous rapid growth of strong magnetic fields is rather ubiquitous in high-energy density environments ranging from astrophysical sources (e.g., gamma-ray bursts and relativistic shocks), to reconnection, to laser-plasma interaction laboratory experiments, where they are produced by kinetic streaming instabilities of the Weibel type. Relativistic electrons propagating through these sub-Larmor-scale magnetic fields radiate in the jitter regime, in which the anisotropy of the magnetic fields and the particle distribution have a strong effect on the produced radiation. Here we develop the general theory of jitter radiation, which (1) includes anisotropic magnetic fields and electron velocity distributions, (2) accounts for the effects of trapped electrons, and (3) extends the description to large deflection angles of radiating particles thus establishing a cross-over between the classical jitter and synchrotron regimes. Our results are in remarkable agreement with the radiation spectra obtained from particle-in-cell simulations of the classical Weibel instability. Particularly interesting is the onset of the field growth, when the transient hard synchrotron-violating spectra are common as a result of the dominant role of the trapped population. This effect can serve as a distinct observational signature of the violent field growth in astrophysical sources and lab experiments. It is also interesting that a system with small-scale fields tends to evolve toward the small-angle jitter regime, which can, under certain conditions, dominate the overall emission of a source.

• OSTI ID: 21579955
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 737; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMIC GAMMA BURSTS
COSMIC RADIATION
DISTRIBUTION
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
INSTABILITY
IONIZING RADIATIONS
LEPTONS
MAGNETIC FIELDS
MAGNETIC RECONNECTION
PLASMA
PRIMARY COSMIC RADIATION
RADIATIONS
SIMULATION
TRAPPED ELECTRONS
VELOCITY