Turbulent mixing and nuclear burning in stellar interiors

Miroslav Mocák, Casey Meakin, Simon W. Campbell, W. David Arnett

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

The turbulent burning of nuclei is a common phenomenon in the evolution of stars. Here we examine a challenging case: the merging of the neon and oxygen burning shells in a 23M star. A previously unknown quasi-steady state is established by the interplay between mixing, turbulent transport, and nuclear burning. The resulting stellar structure has two burning shells within a single convection zone. We find that the new neon burning layer covers an extended region of the convection zone, with the burning peak occurring substantially below where the average convective turnover timescale becomes equal to the burning timescale. These characteristics differ from those predicted by 1D stellar evolution models of similar ingestion events. We develop the mean-field turbulence equations that govern compositional evolution, and use them to interpret our data set. An important byproduct is a means to quantify sub-grid-scale effects intrinsic to the numerical hydrodynamic scheme. For implicit large eddy simulations, the analysis method is particularly powerful because it can reveal where and how simulated flows are modified by resolution, and provide straightforward physical interpretations of the effects of dissipation or induced transport. Focusing on the mean-field composition variance equations for our analysis, we recover a Kolmogorov rate of turbulent dissipation without it being imposed, in agreement with previous results which used the turbulent kinetic energy equation.

Original languageEnglish (US)
Pages (from-to)2918-2932
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume481
Issue number3
DOIs
StatePublished - Dec 11 2018

Keywords

  • Hydrodynamics
  • Stars: evolution
  • Stars: interiors
  • Turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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