| Full text | |
| 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: | 13/18815-0 - Magnetic reconnection and related processes in collisional and collisionless astrophysical plasmas: from solar flares to extragalactic sources |
| Grantee: | Grzegorz Kowal |
| Support Opportunities: | Scholarships in Brazil - Young Researchers |
| 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 Opportunities: | Multi-user Equipment Program |
| FAPESP's process: | 11/12909-8 - Magnetic fields, turbulence and plasma effects in the intergalactic medium |
| Grantee: | Diego Antonio Falceta Gonçalves |
| Support Opportunities: | 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 Opportunities: | Research Grants - Young Investigators Grants |
| 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 Opportunities: | 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 Opportunities: | Regular Research Grants |
| FAPESP's process: | 09/50053-8 - Magnetic reconnection and particle acceleration in astrophysical sources and diffuse media |
| Grantee: | Grzegorz Kowal |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |