Varma Vishnu, Müller Bernhard
School of Physics and Astronomy, 10 College Walk, Monash University, Clayton VIC 3800, Australia.
Mon Not R Astron Soc. 2021 Mar 26;504(1):636-647. doi: 10.1093/mnras/stab883. eCollection 2021 Jun.
We present a first 3D magnetohydrodynamic (MHD) simulation of convective oxygen and neon shell burning in a non-rotating [Formula: see text] star shortly before core collapse to study the generation of magnetic fields in supernova progenitors. We also run a purely hydrodynamic control simulation to gauge the impact of the magnetic fields on the convective flow and on convective boundary mixing. After about 17 convective turnover times, the magnetic field is approaching saturation levels in the oxygen shell with an average field strength of [Formula: see text], and does not reach kinetic equipartition. The field remains dominated by small-to-medium scales, and the dipole field strength at the base of the oxygen shell is only [Formula: see text]. The angle-averaged diagonal components of the Maxwell stress tensor mirror those of the Reynolds stress tensor, but are about one order of magnitude smaller. The shear flow at the oxygen-neon shell interface creates relatively strong fields parallel to the convective boundary, which noticeably inhibit the turbulent entrainment of neon into the oxygen shell. The reduced ingestion of neon lowers the nuclear energy generation rate in the oxygen shell and thereby slightly slows down the convective flow. Aside from this indirect effect, we find that magnetic fields do not appreciably alter the flow inside the oxygen shell. We discuss the implications of our results for the subsequent core-collapse supernova and stress the need for longer simulations, resolution studies, and an investigation of non-ideal effects for a better understanding of magnetic fields in supernova progenitors.
我们展示了在核心坍缩前不久，对一颗非旋转的[公式：见原文]恒星中对流氧和氖壳层燃烧的首次三维磁流体动力学（MHD）模拟，以研究超新星前身星中磁场的产生。我们还进行了纯流体动力学控制模拟，以评估磁场对对流流动和对流边界混合的影响。在大约17个对流周转时间后，氧壳层中的磁场接近饱和水平，平均场强为[公式：见原文]，且未达到动能均分。磁场仍以中小尺度为主，氧壳层底部的偶极场强仅为[公式：见原文]。麦克斯韦应力张量的角度平均对角分量与雷诺应力张量的分量相似，但小一个数量级左右。氧 - 氖壳层界面处的剪切流产生了与对流边界平行的相对较强的场，这显著抑制了氖向氧壳层的湍流夹带。氖摄入的减少降低了氧壳层中的核能产生率，从而略微减缓了对流流动。除了这种间接影响外，我们发现磁场并未明显改变氧壳层内的流动。我们讨论了我们的结果对后续核心坍缩超新星的影响，并强调需要进行更长时间的模拟、分辨率研究以及对非理想效应的研究，以便更好地理解超新星前身星中的磁场。
