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Magnetic field amplification and saturation in turbulence behind a relativistic shock

  • We have investigated via 2D relativistic magnetohydrodynamic simulations the long-term evolution of turbulence created by a relativistic shock propagating through an inhomogeneous medium. In the post-shock region, magnetic field is strongly amplified by turbulent motions triggered by pre-shock density inhomogeneities. Using a long-simulation box we have followed the magnetic field amplification until it is fully developed and saturated. The turbulent velocity is subrelativistic even for a strong shock. Magnetic field amplification is controlled by the turbulent motion and saturation occurs when the magnetic energy is comparable to the turbulent kinetic energy. Magnetic field amplification and saturation depend on the initial strength and direction of the magnetic field in the pre-shock medium, and on the shock strength. If the initial magnetic field is perpendicular to the shock normal, the magnetic field is first compressed at the shock and then can be amplified by turbulent motion in the post-shock region. Saturation occurs when theWe have investigated via 2D relativistic magnetohydrodynamic simulations the long-term evolution of turbulence created by a relativistic shock propagating through an inhomogeneous medium. In the post-shock region, magnetic field is strongly amplified by turbulent motions triggered by pre-shock density inhomogeneities. Using a long-simulation box we have followed the magnetic field amplification until it is fully developed and saturated. The turbulent velocity is subrelativistic even for a strong shock. Magnetic field amplification is controlled by the turbulent motion and saturation occurs when the magnetic energy is comparable to the turbulent kinetic energy. Magnetic field amplification and saturation depend on the initial strength and direction of the magnetic field in the pre-shock medium, and on the shock strength. If the initial magnetic field is perpendicular to the shock normal, the magnetic field is first compressed at the shock and then can be amplified by turbulent motion in the post-shock region. Saturation occurs when the magnetic energy becomes comparable to the turbulent kinetic energy in the post-shock region. If the initial magnetic field in the pre-shock medium is strong, the post-shock region becomes turbulent but significant field amplification does not occur. If the magnetic energy after shock compression is larger than the turbulent kinetic energy in the post-shock region, significant field amplification does not occur. We discuss possible applications of our results to gamma-ray bursts and active galactic nuclei.show moreshow less

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Metadaten
Author:Yosuke Mizuno, Martin PohlORCiDGND, Jacek Niemiec, Bing Zhang, Ken-Ichi Nishikawa, Philip E. Hardee
DOI:https://doi.org/10.1093/mnras/stu196
ISSN:0035-8711 (print)
ISSN:1365-2966 (online)
Parent Title (English):Monthly notices of the Royal Astronomical Society
Publisher:Oxford Univ. Press
Place of publication:Oxford
Document Type:Article
Language:English
Year of first Publication:2014
Year of Completion:2014
Release Date:2017/03/27
Tag:MHD; gamma-ray burst: general; methods: numerical; relativistic processes; shock waves; turbulence
Volume:439
Issue:4
Pagenumber:14
First Page:3490
Last Page:3503
Funder:NSF [AST-0908010, AST-0908040, AST-0908362]; NASA [NNX08AG83G, NNX12AH06G]; Taiwan National Science Council [NSC 100-2112-M-007-022-MY3]; Polish National Science Centre [DEC-2011/01/B/ST9/03183, DEC-2012/04/A/ST9/00083]; Helmholtz Alliance for Astroparticle Physics, HAP; Initiative and Networking Fund of the Helmholtz Association; National Science Foundation
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
Peer Review:Referiert