Jeremiah W. Murphy, Joshua C. Dolence, Adam Burrows
Multi-dimensional instabilities have become an important ingredient in core-collapse supernova (CCSN) theory. Therefore, it is necessary to understand the driving mechanism of the dominant instability. Comparing 3D CCSN simulations with turbulence theory, we find that buoyancy-driven convection dominates post-shock turbulence. In general, the convective fluxes and kinetic energies in the neutrino-heated region are consistent with expectations of buoyancy-driven convection. Specifically, the convective flux is positive where buoyancy actively drives convection, and the radial and tangential components of the kinetic energy are in rough equipartition (i.e. K_r ~ K_{\theta} + K_{\phi}). Both results are natural consequences of buoyancy-driven convection, and are commonly observed in simulations of convection in other contexts. Most compelling, though, is the consistency between 3D CCSN simulations and predictions of neutrino-driven convection theory. For one, global buoyant driving is balanced by global turbulent dissipation. Secondly, the convective luminosity and turbulent dissipation are linearly proportional to the driving neutrino power. Thirdly, we accurately calculate the shock radius only if we include turbulent ram pressure in the shock conditions. In all, these results suggest that in neutrino-driven explosions the multi-dimensional motions are consistent with neutrino-driven convection, and there is little need to invoke alternative instabilities such as the standing accretion shock instability.
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http://arxiv.org/abs/1205.3491
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