Thomson scattering optical depth of TI zones, plotted against the radial distance from the BH of the mass M_BH = 10⁸ M_⊙, and shown for three values of magnetic parameters M1, M2, and M3 (from left to right columns), and an accretion rate of ṁ = 0.012, 0.27, and 0.1 (from upper to bottom rows). The photosphere is marked using the green dashed line, temperature minimum with a thick black solid line, thermalization depth (τ * = 1) with a red dotted line. The extent of the thermal instability is presented as a pink-filled area.