We suggest that the hysteretic cycle of black hole state transitions arises from two established properties of accretion disks : the increase in turbulent stress in disks threaded by a net magnetic field and the ability of thick ( but not thin ) disks to advect such a field radially .
During quiescence , magnetic field loops are generated by the magnetorotational instability at the interface between the inner hot flow and outer thin disk .
Vertical flux is advected into and accumulates stochastically within the inner flow , where it stimulates the turbulence so that \alpha \sim 1 .
The transition to a geometrically thin inner disk occurs when L \sim \alpha ^ { 2 } L _ { Edd } \sim L _ { Edd } , and the first “ thin ” disk to form is itself moderately thick , strongly magnetized , and able to advect field inward .
These properties favor episodic jet production .
As the accretion rate declines magnetic flux escapes , \alpha decreases to \alpha \sim 0.01 - 0.1 , and a hot inner flow is not re-established until L \ll L _ { Edd } .
We discuss possible observational consequences of our scenario .