Vertical structure of the accreting two-temperature corona and the transition to an ADAF

We investigate the model of the disc/corona accretion flow around the black hole. Hot accreting advective corona is described by the two-temperature p lasma in pressure equilibrium with the cold disk. Corona is powered by accr etion but it also exchanges energy with the disk through the radiative inte raction and conduction. The model, parameterized by the total (i.e. disk pl us corona accretion rate, (m) over dot and the viscosity parameter, a, uniq uely determines the fraction of energy released in the corona as a function of radius and. in particular, the transition radius to the single-phase fl ow. Self-consistent solutions with the mass exchange between phases display rad ial dependence of the parameters qualitatively different from the 'static' case, without the mass exchange. Corona covers the entire disk. The charact er of the radial dependence of the fraction of energy dissipated in the cor ona 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 . Introduction evaporates, changing the accretion pattern into the single hot advection-dominated acc retion flow (ADAF). For intermediate accretion rates the reverse process - condensation - becomes important, allowing possibly for a secondary disc re building in the innermost part of the system. High accretion rates always p re vent the transition into ADAF, and the cold disk extends down to the mar ginally stable orbit. The transition radius, r(tr), between the outer, two-phase flow and the inn er, single-phase, optically thin flow, is equal to 4.51(m)over dot(-4/3)alp ha(0.1)(7)R(Schw) for (m)over dot < 6.9 x 10(-2)alpha(0.1)(3.3) and then co ntracts to the marginally stable orbit in a discontinuous way above this cr itical value of (m)over dot. This model reproduces all characteristic luminosity states of accretion bla ck hole without any additional ad hoc assumptions. In particular the mechan ism of the disk evaporation leads to a new, almost horizontal branch on the accretion how'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 boun daries for the time evolution of unstable, radiation-pressure dominated dis k. Therefore the disk at high accretion rates, corresponding to Very High S tate in GBH and perhaps to Narrow Line Seyfert 1, and quasar stage may osci llate between the disk dominated state and the evaporation branch state, wi th only a weak contribution from the cold disk emission. The position of th is blanch for alpha = 0.08 with respect to the gas pressure dominated branc h 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 considerab ly if monitored in timescales of years. We also suggest a new interpretatio n of the Intermediate State, consistent with the presence of the strong ref lected component.