Temperature versus depth for a model with and a model without energy deposition. Because the total flux must already be present at the inner boundary of the latter model, a higher temperature gradient in the inner region is obtained, showing that not all heating processes are incorporated physically correctly in this case. The fact that except from this innermost region the gradients of the consistently calculated temperature structures are not much different for both types of models is the reason that the characteristic shapes of the SN Ia spectra obtained with and without energy deposition are quite similar (cf. Fig. 18).