湍流云核中圆盘的形成：避免磁制动灾难
Disc formation in turbulent cloud cores: Circumventing the magnetic braking catastrophe
摘要：
我们目前的崩溃模拟强磁化，100 M_太阳，湍流云核。在坍缩过程中形成的原恒星周围，开普勒圆盘的典型大小高达100 AU，与以前忽略湍流的模拟形成对比。通过分析凝聚形成的圆盘，我们发现磁通量损失不足以解释开普勒圆盘的形成。平均磁场强烈地倾向于盘，这可能降低磁制动效率。然而，磁制动效率降低的主要原因是盘周围的高度无序的磁场。此外，由于在盘的湍流环境中缺乏相干旋转结构，所以不能建立角动量提取所需的环形磁场。同时，由于湍流运动产生的局部剪切流，角动量流入保持较高。我们认为，“磁制动灾难”是一个理想化的非湍流的初始条件和湍流提供了一个自然的机制来规避这个问题的人工制品。
英文摘要：
We present collapse simulations of strongly magnetised, 100 M_sun, turbulent cloud cores. Around the protostars formed during the collapse Keplerian discs with typical sizes of up to 100 AU build up in contrast to previous simulations neglecting turbulence. Analysing the condensations in which the discs form, we show that the magnetic flux loss is not sufficient to explain the build-up of Keplerian discs. The average magnetic field is strongly inclined to the disc which might reduce the magnetic braking efficiency. However, the main reason for the reduced magnetic braking efficiency is the highly disordered magnetic field in the surroundings of the discs. Furthermore, due to the lack of a coherently rotating structure in the turbulent environment of the disc no toroidal magnetic field necessary for angular momentum extraction can build up. Simultaneously the angular momentum inflow remains high due to local shear flows created by the turbulent motions. We suggest that the "magnetic braking catastrophe" is an artefact of the idealised non-turbulent initial conditions and that turbulence provides a natural mechanism to circumvent this problem.
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