during the early decay, and is truncated by 20 d due to shadowing. In the outer disk ($\sim6\times10^{10}$ cm), the contribution of the irradiation becomes important. Around maximum, the viscous heating dominates the irradiation. After the cooling wave propagates into the outer region, and this region cools, the irradiation heating, due entirely to indirect irradiation because of shadowing, dominates over the viscous heating. This is shown by the rapid increase in the ratio of irradiation heating to the total heating about 5 d after the maximum in figure 5. The indirect irradiation heating then decreases along with ${\dot M}_{\rm in}$ as the cooling wave propagates inward. The behavior of the outer regions under the effects of radiation is more complicated than reflected in figure 5.

 Global Effects of Irradiation on Decay
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[6]{} [22pc]{} [Time-dependent evolution of the disk mid-plane temperature during the early decay phase (upper panel) and the corresponding states of the gas (lower panel) for the model with no irradiation. “HOT" denotes the hot thermal equilibrium states and “MOLECULE" represents the molecular stagnation stage (see text and figure 1).]{}

[7]{} [22pc]{} [Time-dependent evolution of the disk mid-plane temperature during the early decay phase (upper panel) and the 