Scatter plots showing the relationship between internal heating (log q_h) inside warm corona with hot corona spectral index Γ_hc (a), optical depth (τ_cor) of warm corona with Γ_hc (b), and variation of log q_h vs. τ_cor (c). The best fit linear regression is indicated by a grey dashed line. The grey solid curve in the top-right panel corresponds to χ = 1 (Eq. (5)), marking the boundary between active χ < 1, and passive disk with χ > 1. Different symbols associated with sources are given in the bottom right.