坍缩的致密核心中的磁性过程。II片段化。是否存在碎片化危机？
Magnetic processes in a collapsing dense core. II Fragmentation. Is there a fragmentation crisis ?
摘要：
节录。很大一部分恒星是在双星系统中发现的。因此，研究致密分子核心的碎裂对于我们理解恒星形成过程是很重要的。我们研究了磁场的影响，理想地耦合到气体，在多个系统的崩溃核心的破碎。我们提出了高分辨率的数值模拟与RAMSES MHD代码开始与一个均匀的球体在固体旋转和一个均匀的磁场平行于旋转轴。我们特别注意的强度的磁场和解释的结果，使用的分析在一个配套文件。结果在很大程度上取决于最初播种的扰动的幅度$A$。对于一个低的振幅，$A=0.1$，我们发现，超过临界质量-通量比，$μ$，高达$μ= 20$，离心支撑的磁盘，在流体动力学的情况下，碎片的质量-通量的值是稳定的，并保持轴对称。详细的研究表明，这是由于快速增长的环形磁场诱导的磁盘内的微分运动。对于$μ$值较小的$\simeq 5$，对应于较大的磁场强度，由于磁制动，没有离心支撑的磁盘。当扰动的幅度等于$A=0.5$时，每个初始峰独立地发展，并且核心碎片为大范围的$μ$。只有当$μ$的值接近1时，磁场才能够防止碎裂。由于大部分恒星是双星，低磁场强度的结果阻止了在弱扰动情况下的碎裂，这是有问题的。我们讨论了三种可能的机制...
英文摘要：
Abridged. A large fraction of stars are found in binary systems. It is therefore important for our understanding of the star formation process, to investigate the fragmentation of dense molecular cores. We study the influence of the magnetic field, ideally coupled to the gas, on the fragmentation in multiple systems of collapsing cores. We present high resolution numerical simulations performed with the RAMSES MHD code starting with a uniform sphere in solid body rotation and a uniform magnetic field parallel to the rotation axis. We pay particular attention to the strength of the magnetic field and interpret the results using the analysis presented in a companion paper. The results depend much on the amplitude, $A$, of the perturbations seeded initially. For a low amplitude, $A=0.1$, we find that for values of the mass-to-flux over critical mass-to-flux ratio, $μ$, as high as $μ= 20$, the centrifugally supported disk which fragments in the hydrodynamical case, is stabilized and remains axisymmetric. Detailed investigations reveals that this is due to the rapid growth of the toroidal magnetic field induced by the differential motions within the disk. For values of $μ$ smaller $\simeq 5$, corresponding to larger magnetic intensities, there is no centrifugally supported disk because of magnetic braking. When the amplitude of the perturbation is equal to $A=0.5$, each initial peak develops independently and the core fragments for a large range of $μ$. Only for values of $μ$ close to 1 is the magnetic field able to prevent the fragmentation. Since a large fraction of stars are binaries, the results of low magnetic intensities preventing the fragmentation in case of weak perturbations, is problematic. We discuss three possible mechanisms...
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