2002/11/10 by Eric G. Blackman, Blackman, Eric G.
Physics and Astronomy · #Astro and Planetary Science #Astrophysics (astro-ph) #FOS: Physical sciences #Gamma-ray bursts and supernovae #Solar and Space Plasma Dynamics #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0211187
12 pages LaTeX (Q&A at end), to appear in proceedings of the 1st Niels Bohr Summer Institute: "Beaming and Jets in Gamma-Ray Bursts", Copenhagen, Aug 2002
openalex publication_date 2002/11/10 · arxiv created 2002/11/12 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Magnetic fields play a dual role in gamma-ray bursts (GRBs). First, GRB and afterglow spectra (the latter interpreted as emission from external shocks) imply synchrotron radiation in a magnetic field that is a significant fraction of equipartition with the particle energy density. Second, magnetized rotators with ∼ 1015 Gauss field may power GRB by transporting Poynting flux to large distances where it dissipates and also drives an external shock. The field amplification at external shocks and in the engine involve separate processes. External shock fields are likely either seeded by a pre-GRB wind, or are amplified by two-stream plasma instabilities with MHD turbulence playing a subsequent role. In the engine, the large scale fields are likely produced by MHD helical dynamos, since flux accretion cannot easily compete with turbulent diffusion, and because structures must be large enough to rise to coronae before diffusing. Why helical dynamos are feasible, and their relation to the magnetorotational instability are among the points discussed.