A large-scale closed magnetic field can transfer angular momentum and energy between a black hole ( BH ) and its surrounding accretion flow .
We investigate the effects of this magnetic coupling ( MC ) process on the dynamics of a hot accretion flow ( e.g. , an advection dominated accretion flow , hereafter ADAF ) .
The energy and angular momentum fluxes transported by the magnetic field are derived by an equivalent circuit approach .
For a rapidly rotating BH , it is found that the radial velocity and the electron temperature of the accretion flow decrease , whereas the ion temperature and the surface density increase .
The significance of the MC effects depends on the value of the viscous parameter \alpha .
The effects are obvious for \alpha = 0.3 but nearly ignorable for \alpha = 0.1 .
For a BH with specific angular momentum , a _ { * } = 0.9 , and \alpha = 0.3 , we find that for reasonable parameters the radiative efficiency of a hot accretion flow can be increased by \sim 30 \% .