A jet acceleration mechanism for the black hole disk system

Abstract

A jet acceleration mechanism of extracting energy from the disk-corona surrounding a rotating black hole is proposed. In this disk-corona scenario, the central object is a rotating Kerr black hole, and a geometrically thin and optically thick disk is sandwiched by a slab corona. The large-scaled magnetic field plays an important role in jet acceleration mechanism. So we obtain the value of the magnetic field in such a disk-corona system by solving the disk dynamic equations in the context of general relativity. The results show that the value of magnetic field decreases with the increase of disk radius, while increases with the increase of black hole spin parameter a*. Then the analytical expression of the jet power is derived based on the electronic circuit theory of the magnetosphere. It is found that the jet power increases obviously with increasing black hole spin parameter a* and magnetic stress parameter . Furthermore, the calculation results also show that the jet power is mainly from the inner region of the disk-corona system, which is consistent with the observations of the jet. Finally, a sample composed of the 23 Fermi blazars with high jet power is used to explore our jet production mechanism. The conclusion suggests that our jet acceleration mechanism can simulate all sources with high power jet. By comparing with the observational data, we find that these high jet power sources cannot be explained by the Blandford-Znajek mechanism, even if the central object is extreme Kerr black hole.