The magnetorotational instability in core-collapse supernova explosions
The magnetorotational instability in core-collapse supernova explosions
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DOI：
10.1086/344135
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发表时间：
2003-02-20
影响因子：
4.9
通讯作者：
Lichtenstadt, I
中科院分区：
文献类型：
--
作者：
Akiyama, S;Wheeler, JC;Lichtenstadt, I
我们研究了铁芯塌陷背景下磁旋转不稳定性（MRI）的作用。 MRI 的场在时间尺度 Omega(-1) 上的指数增长将主导具有相同特征时间的场线“包裹”的线性增长过程。我们研究了与文献中的模型相对应的各种初始旋转状态，包括固体旋转或旋转速度梯度。相对适中的初始旋转值（类似于 10 秒的周期）将产生非常快速旋转的原中子星，因此相对于下落物质会产生强烈的差动旋转。我们假设球壳上角动量守恒。在后续的旋转速度计算中忽略旋转畸变和磁场的动态反馈。在我们的旋转和塌陷条件下，种子场预计会被 MRI 放大并呈指数增长至饱和场。讨论了两个饱和场示例的结果，一个对应于 v(A) = rOmega 的基准场和一个对应于 MRI 最大生长模式的场。正如预期的那样，我们发现新形成的原中子星边界处的剪切力很强，并且出乎意料的是，失速激波内的区域可能会受到强烈的 MHD 活动的影响。铁芯的适度初始旋转速度会导致亚开普勒旋转和亚均分磁场，但仍会产生大量 MHD 光度和环向应力：10(15)-10(16) G 阶的饱和场可以在反弹后约 300 ms 发展，相关 MHD 光度类似于 10(52) ergs(-1)。由这种 MHD 能量驱动的双极流可以影响甚至引起与核心塌陷超新星相关的爆炸。
We investigate the action of the magnetorotational instability (MRI) in the context of iron-core collapse. Exponential growth of the field on the timescale Omega(-1) by the MRI will dominate the linear growth process of field-line "wrapping" with the same characteristic time. We examine a variety of initial rotation states, with solid-body rotation or a gradient in rotational velocity, that correspond to models in the literature. A relatively modest value of the initial rotation, a period of similar to10 s, will give a very rapidly rotating proto neutron star and hence strong differential rotation with respect to the infalling matter. We assume conservation of angular momentum on spherical shells. Rotational distortion and the dynamic feedback of the magnetic field are neglected in the subsequent calculation of rotational velocities. In our rotating and collapsing conditions, a seed field is expected to be amplified by the MRI and to grow exponentially to a saturation field. Results are discussed for two examples of saturation fields, a fiducial field that corresponds to v(A) = rOmega and a field that corresponds to the maximum growing mode of the MRI. We find, as expected, that the shear is strong at the boundary of the newly formed proto neutron star and, unexpectedly, that the region within the stalled shock can be subject to strong MHD activity. Modest initial rotation velocities of the iron core result in sub-Keplerian rotation and a sub-equipartition magnetic field that nevertheless produce substantial MHD luminosity and hoop stresses: saturation fields of order 10(15)-10(16) G can develop similar to300 ms after bounce with an associated MHD luminosity of similar to10(52) ergs s(-1). Bipolar flows driven by this MHD power can affect or even cause the explosions associated with core-collapse supernovae.