Investigation on the Quasi-Cycle of Black Hole Spin

A reverse condition of accretion flow and its constraints on black hole spin in the quasi-cycle are proposed. It is shown that the necessary condition for the quasi-cycle is that the closed magnetic field lines must dominate over the open ones at the horizon. The efficiency of converting accreted rest mass into radiation energy in the quasi-cycle is proved to increase as the strength of the magnetic transfer process. In addition, a general expression for the efficiency is derived.