Equilibrium curves for discs around stellar-mass BH (left panel) and SMBH (right panel). In each panel, the ξ-curves are constructed for two values of the turbulent parameter α: 0.1 and 0.01. The solid lines are calculated by ALPHADISC and their upper dotted tails correspond to P_rad > P_gas. Analytic relations in the radiation-pressure regime (A zone, dashed, ∝Σ⁻¹) and the advective regime (dash-dotted, ∝Σ) are calculated using Eqs. (B.5) and (B.4), respectively. The dots mark critical points for the geometrically thin states: the minimum and the maximum surface density, Σ⁺ and Σ_A, in the ionised state and the maximum surface density Σ⁻ in the recombined state The arrows schematically show the direction of ring heating due to ionisation instability. At the same time, α increases.