Structured coronae of accretion disks
Abstract
A model based on the amplification of magnetic fields by convective motions and differential rotation within a hot (no less than about 1,000,000 K) accretion disk is developed for the fluctuating hard component of intense cosmic X-ray sources such as Cyg X-1. It is shown that field reconnection within the inner portion of the disk is ineffective in limiting field amplification. Magnetic fields may therefore reach strengths comparable to the equipartition value, leading to their emergence through buoyancy in the form of looplike structures and resulting in a very hot (over 100 million K) magnetically confined structured corona similar to the observed structure of solar corona. In particular, the soft X-ray luminosity of the accretion disk determines the dominant energy loss mechanism in loops.