Non-ideal magnetohydrodynamics (MHD) is the dominant process. We investigate the effect of magnetic fields (ideal and non-ideal) and turbulence (suband transsonic) on the formation of circumstellar discs that form nearly simultaneously with the formation of the protostar. This is done by modelling the gravitational collapse of a 1 M⊙ gas cloud that is threaded with a magnetic field and imposed with both rotational and turbulent velocities. We investigate magnetic fields that are parallel/anti-parallel and perpendicular to the rotation axis, two rotation rates and four Mach numbers. Disc formation occurs preferentially in the models that include non-ideal MHD where the magnetic field is anti-parallel or perpendicular to the rotation axis. This is independent of the initial rotation rate and level of turbulence, suggesting that subsonic turbulence plays a minimal role in influencing the formation of discs. Aside from first core outflows which are influenced by the initial level of turbulence, non-ideal MHD processes are more important than turbulent processes during the formation of discs around low-mass stars.

中文翻译：

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非理想磁流体动力学与湍流——I. 哪个是原恒星盘形成的主要过程？

非理想磁流体动力学 (MHD) 是主要过程。我们研究了磁场（理想和非理想）和湍流（亚音速和超音速）对几乎与原恒星形成同时形成的星周盘形成的影响。这是通过对 1 M⊙ 气体云的引力坍缩进行建模来完成的，该气体云带有磁场并受到旋转和湍流速度的影响。我们研究平行/反平行和垂直于旋转轴的磁场、两个旋转速率和四个马赫数。圆盘形成优先出现在包含非理想 MHD 的模型中，其中磁场与旋转轴反平行或垂直。这与初始旋转速率和湍流水平无关，表明亚音速湍流在影响圆盘形成方面的作用很小。除了受初始湍流水平影响的第一核外流之外，在低质量恒星周围盘形成期间，非理想 MHD 过程比湍流过程更重要。