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The delayed detonation model describes the observational properties of themajority of type Ia supernovae very well. Using numerical data from athree-dimensional deflagration model for type Ia supernovae, the intermittencyof the turbulent velocity field and its implications on the probability of adeflagration-to-detonation (DDT) transition are investigated. From structurefunctions of the turbulent velocity fluctuations, we determine intermittencyparameters based on the log-normal and the log-Poisson models. On the otherhand, the analysis of the turbulent velocity fluctuations in the vicinity ofthe flame front by Roepke suggests a much higher probability of large velocityfluctuations on the grid scale in comparison to the log-normal intermittencymodel. Following Pan et al., we computed probability density functions for aDDT for the different distributions. Assuming that a DDT can occur in thestirred flame regime, as proposed by Woosley et al., the log-normal model wouldimply a delayed detonation between 0.7 and 0.8 seconds after the beginning ofthe deflagration phase for the multi-spot ignition scenario used in thesimulation. However, the probability drops to virtually zero if a DDT isfurther constrained by the requirement that the turbulent velocity fluctuationsreach about 500 km/s. Under this condition, delayed detonations are onlypossible if the distribution of the velocity fluctuations is not log-normal.  From our calculations follows that the distribution obtained by Roepke allowfor multiple DDTs around 0.8 seconds after ignition at a transition densityclose to 1x10^7 g/cm^3.

Turbulence in a 3D deflagration model for type Ia SNe: II. Intermittency and the deflagration-to-detonation transition probability