On the Blandford-Znajek mechanism of the energy loss of a rotating black hole

The Grad-Shafranov approach to the problem of the structure of the black-ho le magnetosphere is discussed. For the double transonic flow, the number of boundary conditions in the pair creation region is shown to be sufficient to determine not only the longitudinal electric current, but also the angul ar velocity of a flow as a solution to a problem. As a result, the energy l oss is determined by the physical parameters at the particle creation regio n rather than the "boundary conditions" at the event horizon.