We investigate the model of the disc/corona accretion flow around the black hole .
Hot accreting advective corona is described by the two-temperature plasma in pressure equilibrium with the cold disk .
Corona is powered by accretion but it also exchanges energy with the disk through the radiative interaction and conduction .
The model , parameterized by the total ( i.e .
disk plus corona ) accretion rate , \dot { m } and the viscosity parameter , \alpha , uniquely determines the fraction of energy released in the corona as a function of radius and , in particular , the transition radius to the single-phase flow .

Self-consistent solutions with the mass exchange between phases display radial dependence of the parameters qualitatively different from the ’ static ’ case , without the mass exchange .
Corona covers the entire disk .
The character of the radial dependence of the fraction of energy dissipated in the corona is qualitatively different for low and high total accretion rate .

If the total accretion rate is low , the corona becomes stronger towards the central object , and finally the disc completely evaporates , changing the accretion pattern into the single hot advection-dominated accretion flow ( ADAF ) .
For intermediate accretion rates the reverse process - condensation - becomes important , allowing possibly for a secondary disc rebuilding in the innermost part of the system .
High accretion rates always prevent the transition into ADAF , and the cold disk extends down to the marginally stable orbit .

The transition radius , r _ { tr } , between the outer , two-phase flow and the inner , single-phase , optically thin flow , is equal to 4.51 \dot { m } ^ { -4 / 3 } \alpha _ { 0.1 } ^ { 7 } R _ { Schw } for \dot { m } < 6.9 \times 10 ^ { -2 } \alpha _ { 0.1 } ^ { 3.3 } and then contracts to the marginally stable orbit in a discontinuous way above this critical value of \dot { m } ..

This model reproduces all characteristic luminosity states of accretion black hole without any additional ad hoc assumptions .
In particular .
the mechanism of the disk evaporation leads to a new , almost horizontal branch on the accretion flow ’ s stability curve ( i.e .
the dependence of accretion rate on surface density ) at the critical accretion rate .
This branch , together with the upper , advection dominated branch for optically thick disks , form boundaries for the time evolution of unstable , radiation pressure dominated disk .
Therefore the disk at high accretion rates , corresponding to Very High State in GBH and perhaps to Narrow Line Seyfert 1 , and quasar stage may oscillate between the disk dominated state and the evaporation branch state , with only a weak contribution from the cold disk emission .
The position of this branch for \alpha = 0.1 with respect to the gas pressure dominated branch is consistent with the presence of only weakly variable High State in GBH and the absence of a similar state in AGN : all the quasars vary considerably if monitored in timescales of years .
We also suggest a new interpretation of the Intermediate State , consistent with the presence of the strong reflected component .