corresponding states of the gas (lower panel) for the model with both direct and indirect irradiation. “HOT" denotes the hot thermal equilibrium states “Partial Ionization" means that the disk is in the metastable ionization stagnation stage, and “MOLECULE" (or “M") represents the molecular stagnation stage. “Intermediate State" (or “i") denotes the intermediate state between the molecular and partially ionized region (see text and figure 1).]{}

The influence of mild irradiation is not restricted to a small modification of the light curves. Rather, it causes crucial changes in the local disk structure, as illustrated in figures 6 and 7. The upper panel of figure 6 presents the time-dependent evolution of the disk central temperature in the model [*without irradiation*]{}. This model reproduces the typical decay phase, as shown in numerous other studies of the disk instability. As the cooling wave propagates from the outer to inner radii, the disk makes the transition from the hot to cool state from larger to smaller radii. Note the sharp edges of the rapid transition from the hot to cool state, which represent the cooling wave propagation. The lower panel of figure 6 shows the opacity domains through which the disk evolves. It is basically 