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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Ambient magnetic field amplification in shock fronts of relativistic jets: an application to GRB afterglows

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Author(s):
Rocha da Silva, G. [1] ; Falceta-Goncalves, D. [2, 3] ; Kowal, G. [2] ; de Gouveia Dal Pino, E. M. [1]
Total Authors: 4
Affiliation:
[1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil
[2] Univ Sao Paulo, Escola Artes Ciencias & Humanidades, BR-03828000 Sao Paulo - Brazil
[3] Univ St Andrews, Sch Phys & Astron, SUPA, St Andrews KY16 9SS, Fife - Scotland
Total Affiliations: 3
Document type: Journal article
Source: Monthly Notices of the Royal Astronomical Society; v. 446, n. 1, p. 104-119, JAN 2015.
Web of Science Citations: 6
Abstract

Strong downstream magnetic fields of the order of similar to 1G, with large correlation lengths, are believed to cause the large synchrotron emission at the afterglow phase of gamma-ray bursts (GRBs). Despite the recent theoretical efforts, models have failed to fully explain the amplification of the magnetic field, particularly in a matter-dominated scenario. We revisit the problem by considering the synchrotron emission to occur at the expanding shock front of a weakly magnetized relativistic jet over a magnetized surrounding medium. Analytical estimates and a number of high-resolution 2D relativistic magnetohydrodynamical (RMHD) simulations are provided. Jet opening angles of theta = 0 degrees-20 degrees, and ambient to jet density ratios of 10(-4)-10(2) were considered. We found that most of the amplification is due to compression of the ambient magnetic field at the contact discontinuity between the reverse and forward shocks at the jet head, with substantial pile-up of the magnetic field lines as the jet propagates sweeping the ambient field lines. The pile-up is maximum for theta -> 0, decreasing with theta, but larger than in the spherical blast problem. Values obtained for certain models are able to explain the observed intensities. The maximum correlation lengths found for such strong fields is of l(corr) <= 10(14) cm, 2-6 orders of magnitude larger than the found in previous works. (AU)

FAPESP's process: 11/12909-8 - Magnetic fields, turbulence and plasma effects in the intergalactic medium
Grantee:Diego Antonio Falceta Gonçalves
Support type: Regular Research Grants
FAPESP's process: 13/04073-2 - Magnetic reconnection and related processes in collisional and collisionless astrophysical plasmas: from solar flares to extragalactic sources
Grantee:Grzegorz Kowal
Support type: Research Grants - Young Investigators Grants
FAPESP's process: 09/54006-4 - A computer cluster for the Astronomy Department of the University of São Paulo Institute of Astronomy, Geophysics and Atmospheric Sciences and for the Cruzeiro do Sul University Astrophysics Center
Grantee:Elisabete Maria de Gouveia Dal Pino
Support type: Multi-user Equipment Program
FAPESP's process: 13/18815-0 - Magnetic reconnection and related processes in collisional and collisionless astrophysical plasmas: from solar flares to extragalactic sources
Grantee:Grzegorz Kowal
Support type: Scholarships in Brazil - Young Researchers
FAPESP's process: 09/50053-8 - Magnetic reconnection and particle acceleration in astrophysical sources and diffuse media
Grantee:Grzegorz Kowal
Support type: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 06/50654-3 - Investigation of high energy and plasma astrophysics phenomena: theory, observation, and numerical simulations
Grantee:Elisabete Maria de Gouveia Dal Pino
Support type: Research Projects - Thematic Grants
FAPESP's process: 11/51275-4 - Magnetic field effects and particle acceleration in gamma-ray bursts (GRBs): theory, numerical simulations, and observational prospects
Grantee:Elisabete Maria de Gouveia Dal Pino
Support type: Regular Research Grants