Issues in the Blandford-Znajek Process for GRB Inner Engine

Several issues on the Blandford-Znajek process are discussed to demonstrate that it can be an effective mechanism for powering the gamma ray bursts. Using a simple circuit analysis it is argued that the disk power increases the effective power of the black hole-accretion disk system, although a part of disk power can be dissipated into black hole entropy. Within the framework of the force-free magnetosphere with the strong magnetic field, the magnetically dominated MHD flow is found to support the Blandford-Znajek process and it is demonstrated that the possible magnetic repulsion by the rotating black hole may not affect the efficiency substantially.