An Instability-driven Dynamo for Gamma Ray Bursts

Abstract

We show that an MHD-instability driven dynamo (IDD) operating in a hot accretion disk is capable of generating energetically adequate magnetic flux deposition rates above and below a mildly advective accretion disk structure. The dynamo is driven by the magnetorotational instability (MRI) of a toroidal field in a shear flow and is limited by the buoyancy of `horizontal' flux and by reconnection in the turbulent medium. The efficiency of magnetic energy deposition is estimated to be comparable to the neutrino losses although an MHD collimation mechanism may deem this process a more viable alternative to neutrino-burst-driven models of gamma ray bursts.

arXiv comment4 pages, no figures, to appear in Proc. of the 10^th Annual Maryland October Astrophysics Conference: "Cosmic Explosions". Eds. S. S. Holt and W. W. Zhang (AIP Press) (2nd revision AIP LaTex, extended text and equations)