High-resolution simulations of convection preceding ignition in type Ia supernovae using adaptive mesh refinement

Abstract

We extend our previous three-dimensional, full-star simulations of the final hours of convection preceding ignition in Type Ia supernovae to higher resolution using the adaptive mesh refinement capability of our low Mach number code, MAESTRO. We report the statistics of the ignition of the first flame at an effective 4.34km resolution and general flow field properties at an effective 2.17km resolution. We find that off-center ignition is likely, with radius of 50km most favored and a likely range of 40-75 km. This is consistent with our previous coarser (8.68km resolution) simulations, implying that we have achieved sufficient resolution in our determination of likely ignition radii. The dynamics of the last few hot spots preceding ignition suggest that a multiple ignition scenario is not likely. With improved resolution, we can more clearly see the general flow pattern in the convective region, characterized by a strong outward plume with a lower speed recirculation. We show that the convective core is turbulent with a Kolmogorov spectrum and has a lower turbulent intensity and larger integral length scale than previously thought (on the order of 16kms-1 and 200 km, respectively), and we discuss the potential consequences for the first flames. © 2012. The American Astronomical Society. All rights reserved.