High-Resolution Simulations of Convection Preceding Ignition in Type Ia Supernovae Using Adaptive Mesh Refinement

TL;DR

This study uses high-resolution adaptive mesh refinement simulations to analyze convection and ignition in Type Ia supernovae, revealing likely ignition radii, flow patterns, and turbulence characteristics that inform supernova modeling.

Contribution

The paper advances supernova simulation resolution and provides new insights into ignition locations, flow dynamics, and turbulence spectra in Type Ia supernovae.

Findings

Off-center ignition radius likely between 40 and 75 km.

Convective core exhibits turbulence with a Kolmogorov spectrum.

Turbulent intensity is lower and integral length scale larger than previously estimated.

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 4.34 km resolution, and general flow field properties at an effective 2.17 km resolution. We find that off-center ignition is likely, with radius of 50 km most favored and a likely range of 40 to 75 km. This is consistent with our previous coarser (8.68 km 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 16 km s$^{-1}$ and 200 km, respectively), and we discuss the potential consequences for the first flames.