تقرير
Turbulent dynamo action and its effects on the mixing at the convective boundary of an idealized oxygen-burning shell
| العنوان: | Turbulent dynamo action and its effects on the mixing at the convective boundary of an idealized oxygen-burning shell |
|---|---|
| المؤلفون: | Leidi, G., Andrassy, R., Higl, J., Edelmann, P. V. F., Röpke, F. K. |
| سنة النشر: | 2023 |
| المجموعة: | Astrophysics Physics (Other) |
| مصطلحات موضوعية: | Astrophysics - Solar and Stellar Astrophysics, Physics - Plasma Physics |
| الوصف: | 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 the structure and evolution of the star. Under some conditions, strong magnetic fields can be sustained by the action of a turbulent dynamo, adding another layer of complexity and possibly altering the dynamics in the convection zone and at its boundaries. In this study, we used our fully compressible Seven-League Hydro code to run detailed and highly resolved three-dimensional magnetohydrodynamic simulations of turbulent convection, dynamo amplification, and convective boundary mixing in a simplified setup whose stratification is similar to that of an oxygen-burning shell in a star with an initial mass of $25\ M_\odot$. We find that the random stretching of magnetic field lines by fluid motions in the inertial range of the turbulent spectrum (i.e., a small-scale dynamo) naturally amplifies the seed field by several orders of magnitude in a few convective turnover timescales. During the subsequent saturated regime, the magnetic-to-kinetic energy ratio inside the convective shell reaches values as high as $0.33$, and the average magnetic field strength is ${\sim}10^{10}\,\mathrm{G}$. Such strong fields efficiently suppress shear instabilities, which feed the turbulent cascade of kinetic energy, on a wide range of spatial scales. The resulting convective flows are characterized by thread-like structures that extend over a large fraction of the convective shell. The reduced flow speeds and the presence of magnetic fields with strengths up to $60\%$ of the equipartition value at the upper convective boundary diminish the rate of mass entrainment from the stable layer by ${\approx}\,20\%$ as compared to the purely hydrodynamic case. |
| نوع الوثيقة: | Working Paper |
| URL الوصول: | http://arxiv.org/abs/2309.17225 |
| رقم الأكسشن: | edsarx.2309.17225 |
| قاعدة البيانات: | arXiv |
| الوصف غير متاح. |