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

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

2009-11-23

arxiv.org/abs/0911.4345v1

Astronomy and Astrophysics

Astrophysics

High Energy Astrophysical Phenomena

33 pages, 10 figures, submitted to ApJ

Scientific paper

The delayed detonation model describes the observational properties of the majority of type Ia supernovae very well. Using numerical data from a three-dimensional deflagration model for type Ia supernovae, the intermittency of the turbulent velocity field and its implications on the probability of a deflagration-to-detonation (DDT) transition are investigated. From structure functions of the turbulent velocity fluctuations, we determine intermittency parameters based on the log-normal and the log-Poisson models. On the other hand, the analysis of the turbulent velocity fluctuations in the vicinity of the flame front by Roepke suggests a much higher probability of large velocity fluctuations on the grid scale in comparison to the log-normal intermittency model. Following Pan et al., we computed probability density functions for a DDT for the different distributions. Assuming that a DDT can occur in the stirred flame regime, as proposed by Woosley et al., the log-normal model would imply a delayed detonation between 0.7 and 0.8 seconds after the beginning of the deflagration phase for the multi-spot ignition scenario used in the simulation. However, the probability drops to virtually zero if a DDT is further constrained by the requirement that the turbulent velocity fluctuations reach about 500 km/s. Under this condition, delayed detonations are only possible if the distribution of the velocity fluctuations is not log-normal. From our calculations follows that the distribution obtained by Roepke allow for multiple DDTs around 0.8 seconds after ignition at a transition density close to 1x10^7 g/cm^3.

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