EDP Sciences Journals List
Advanced Search
Subscriber Authentication Point
Home All issues Volume 369/2 Article
Free access article

Issue A&A
Volume 369, Number 2, April II 2001
Page(s) 694 - 705
Section Physical and chemical processes
DOI http://dx.doi.org/10.1051/0004-6361:20010131



A&A 369, 694-705 (2001)
DOI: 10.1051/0004-6361:20010131

Large scale magnetic fields and their dissipation in GRB fireballs

H. C. Spruit, F. Daigne and G. Drenkhahn

Max-Planck-Institut für Astrophysik, Postfach 1317, 85741 Garching bei München, Germany

(Received 21 April 2000 / Accepted 17 January 2001 )

Abstract
We consider possible geometries of magnetic fields in GRB outflows, and their evolution with distance from the source. For magnetically driven outflows, with an assumed ratio of magnetic to kinetic energy density of order unity, the field strengths are sufficient for efficient production of $\gamma$-rays by synchrotron emission in the standard internal shock scenario, without the need for local generation of small scale fields. In these conditions, the MHD approximation is valid to large distances ($\ga$1019 cm). In outflows driven by nonaxisymmetric magnetic fields, changes of direction of the field cause dissipation of magnetic energy by reconnection. Much of this dissipation takes place outside the photosphere of the outflow, and can convert a significant fraction of the magnetic energy flux into radiation.


Key words: gamma-ray bursts -- magnetic fields -- radiation mechanisms: nonthermal -- shock waves

Offprint request: H. C. Spruit, henk@mpa-garching.mpg.de




© ESO 2001


What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.