Turbulent dynamo action and its effects on the mixing at the convective boundary of an idealized oxygen-burning shell

• DOI: 10.48550/arxiv.2309.17225
• Publication Date: 2023-01-01
• Authors: Giovanni Leidi; Róbert Andrássy; J. Higl; P. V. F. Edelmann; F. K. Röpke
• Keywords: Convection cell; Convective mixing

Convection is one of the most important mixing processes in stellar interiors. Hydrodynamic mass entrainment can bring fresh fuel from neighboring stable layers into a convection zone, modifying structure and evolution star. Under some conditions, strong magnetic fields be sustained by action turbulent dynamo, adding another layer complexity possibly altering dynamics zone at its boundaries. In this study, we used our fully compressible Seven-League Hydro code to run detailed highly resolved three-dimensional magnetohydrodynamic simulations convection, dynamo amplification, convective boundary simplified setup whose stratification similar that an oxygen-burning shell star with initial $25\ M_\odot$. We find random stretching field lines fluid motions inertial range spectrum (i.e., small-scale dynamo) naturally amplifies seed several orders magnitude few turnover timescales. During subsequent saturated regime, magnetic-to-kinetic energy ratio inside reaches values as high $0.33$, average strength ${\sim}10^{10}\,\mathrm{G}$. Such efficiently suppress shear instabilities, which feed cascade kinetic energy, on wide spatial scales. The resulting flows are characterized thread-like structures extend over large fraction shell. reduced flow speeds presence strengths up $60\%$ equipartition value upper diminish rate ${\approx}\,20\%$ compared purely hydrodynamic case.