cooling becomes essential soon after the onset of the envelope expansion. In the optimal model this transition time is nearly 0.93 days.

Scattering processes are fundamentally nonlocal and result in exceeding the color temperature over the effective one when they are dominant (Mihalas [@m78]; Sobolev [@s80]). During the shock breakout, the adiabatic cooling phase and the CRW phase scattering processes dominate those of true absorption near the photospheric level in the ejecta of the optimal model and, as a consequence, lead to a color temperature that is considerably higher than the effective temperature. Figure \[fig:swbrck\]b shows that the maximum of the color temperature coincides very closely in time with the local minimum of the photospheric radius at day 0.8802 and comes before the maximum of the effective temperature and the bolometric luminosity.

Adiabatic cooling phase {#sec:dmd-adbcln}
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During the shock passage throughout the star, the gas is heated up to about $10^{5}$ K and, as a consequence, is totally ionized. Both the internal gas energy and the radiation energy increase in the SN envelope. After the shock breakout, a dominant process in the subphotospheric, optically thick layers of the expelled envelope is the cooling by adiabatic expansion. The adiabatic losses 