Disk formation during collapse of magnetized protostellar cores
Disk formation during collapse of magnetized protostellar cores
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DOI：
10.1051/0004-6361/200913008
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发表时间：
2009-09
影响因子：
6.5
通讯作者：
P. Hennebelle;Andrea Ciardi
中科院分区：
文献类型：
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作者：
P. Hennebelle;Andrea Ciardi
上下文在星星和行星形成的背景下，理解盘的形成是至关重要的。目标。先前的研究发现，磁场对星前云的坍缩有非常强烈的影响，即使是相对适度的磁场强度也可能抑制圆盘的形成。由于观测推断核心具有相当大的磁化强度，这就提出了磁盘如何形成的问题。然而，大多数研究仅限于磁场与旋转轴之间的初始角度α等于0°的情况。在这里，我们探讨和分析的影响，非对齐的配置磁盘的形成。方法.对不同μ值、不同质量通量比与临界质量通量比以及不同α值的三维理想MHD、AMR进行了数值模拟。结果我们发现，当α从0 °增加到90°时，圆盘更容易形成。我们认为，随着α的增加，磁化赝盘变厚，磁制动效率降低。我们还发现，即使很小的α值（10 -20°）也显示出与对齐情况的显著差异。结论.在理想磁流体力学的框架内，对于我们选择的初始条件，当磁场和旋转轴垂直时，μ值小于3，当它们完全对齐时，μ值小于5 -10时，离心支撑盘不能形成。
Context. In the context of star and planet formation, understanding the formation of disks is of fundamental importance. Aims. Previous studies found that the magnetic field has a very strong impact on the collapse of a prestellar cloud, by possibly suppressing the formation of a disk even for relatively modest values of the magnetic intensity. Since observations infer that cores have a substantial level of magnetization, this raises the question of how disks form. However, most studies have been restricted to the case in which the initial angle, α , between the magnetic field and the rotation axis equals 0°. Here we explore and analyse the influence of non aligned configurations on disk formation. Methods. We perform 3D ideal MHD, AMR numerical simulations for various values of μ , the ratio of the mass-to-flux to the critical mass-to-flux, and various values of α . Results. We find that disks form more easily as α increases from 0 to 90°. We propose that as the magnetized pseudo-disks become thicker with increasing α , the magnetic braking efficiency is lowered. We also find that even small values of α ($\simeq$10–20°) show significant differences with the aligned case. Conclusions. Within the framework of ideal MHD, and for our choice of initial conditions, centrifugally supported disks cannot form for values of μ smaller than $\simeq$3 when the magnetic field and the rotation axis are perpendicular, and smaller than about $\simeq$5–10 when they are perfectly aligned.