1969) and fails to produce the strong intermediate-mass element features observed in SNe Ia. Thus, the explosion should start with a subsonic deflagration flame. The deflagration stage may last until the end of the explosion (the deflagration model; Nomoto et al. 1984), while it is also possible that the deflagration flame turns into the detonation wave \[the delayed detonation model, or the deflagration-detonation transition (DDT) model; Khokhlov 1991; Yamaoka et al. 1992; Woosley & Weaver 1994; Iwamoto et al. 1999\].

The supernova explosion phase has been investigated by “classical” one-dimensional spherically symmetric models; the classical deflagration W7 model of Nomoto et al. (1984) has successfully explained the basic contribution of SNe Ia to Galactic chemical evolution, as well as basic features of observed spectra and light curves of individual SNe Ia of a normal class (Branch et al. 1985). Some improvement in these observational aspects has been obtained by introducing a delayed detonation (e.g., Höflich & Khokhlov 1996; Iwamoto et al. 1999).

These models, however, treat the propagation speed of the deflagration flame as a parameter. Moreover, the deflagration flame is hydrodynamically unstable and non-sphericity is thus actually essential (e.g., Niemeyer et al. 1996). Recent investigations of the explosion models 