The Large-scale Magnetic Fields of Advection-dominated Accretion Flows

摘要: We calculate the advection/diffusion of large-scale magnetic field threading an advection-dominated accretion flow (ADAF) and find that can be dragged inward by efficiently if Prandtl number P-m = eta/nu similar to 1. This is due large radial velocity ADAF. It found pressure as high 50% gas in inner region ADAF close black hole horizon, even external imposed homogeneous vertical strength less than or 5% at outer radius ADAF, which caused plunging rapidly within marginal stable circular orbit. In significantly pressured direction fields, therefore its two orders magnitude higher without fields. means near underestimated assuming equipartition between with conventional model. Our results show horizon more one order 3R(g) (R-g 2GM/c(2)), implies Blandford-Znajek mechanism could important Blandford-Payne for ADAFs. decelerated when strong enough low radius, both. corresponds a critical rate, below will arrested given field. this case, may accrete magnetically confined blobs diffusing through lines very those compact stars. calculations are also valid case connects cold thin disk certain radius. advection fields quite inefficient velocity, thread almost vertically, while these motion