THE BLAST-WAVE-DRIVEN INSTABILITY AS A VEHICLE FOR UNDERSTANDING SUPERNOVA EXPLOSION STRUCTURE

Blast-wave-driven instabilities play a rich and varied role in supernovae (SNe) evolution from explosion to remnant, but interpreting their role is difficult due to the enormous complexity of stellar systems. We consider the simpler idealized problem of an interface between two constant-density fluids perturbed from spherical and driven by a central blast wave. Where valid, the existence of unified solutions suggests that general conclusions can be drawn about the likely asymptotic structure of the mixing zone. To this end, we apply buoyancy-drag and bubble merger models that include effects of divergence and compressibility. In general, these effects preclude the true self-similar evolution of classical Rayleigh-Taylor (RT), but can be incorporated into a quasi-self-similar growth model. Loss of memory of initial conditions (ICs) can occur in the model, but requires pre-explosion mode numbers higher than predicted for Type II SNe, suggesting that their late-time structure is influenced by details of the initial perturbations. Where low modes dominate, as in the Type Ia Tycho remnant, they result from initial perturbations rather than generation from smaller scales. Therefore, the structure observed now contains direct information about the explosion process. When large-amplitude modes exist in the ICs, the contribution from the Richtmyer-Meshkov (RM) instability is significant compared to RT. Such RM growth can yield proximity of the forward shock to the growing spikes and structure that strongly resembles that observed in Tycho. Laser-driven laboratory experiments offer a promising avenue for testing model and simulation descriptions of blast-wave-driven instabilities and making connections to their astrophysical counterparts.