MG14 - Talk detail

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Abstract

Powerful magnetic fields threading a newly formed black hole provide a promising central engine for GRBs. Yet, in binary neutron star mergers and possibly in collapsars the progenitor may not contain sufficient magnetic flux to power bursts of the observed power. I argue that the magnetic fields required to launch the GRB jet can be produced locally in the accretion disk. I will present GRMHD simulations that demonstrate that large-scale jets can be produced by magnetized loops that emerge close to the inner edge of the disk. Accretion of these magnetized loops to the black hole can lead to variable and powerful magnetically dominated jets. The central engine, in this scenario, imprints small-scale magnetic fields into the jet flow. When the jet expands at a scale comparable to or larger than its Thomson photosphere, the magnetic field can dissipate effectively through magnetic reconnection and power the jet emission. Using first principle plasma simulations I argue that the reconnection process is characterized by high dissipative efficiency and predicts that the emission regions are characterized by rough equipartition between radiating particles and magnetic fields.

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