Origin of misalignments: protostellar jet, outflow, circumstellar disc, and magnetic field
Origin of misalignments: protostellar jet, outflow, circumstellar disc, and magnetic field
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错位的起源：原恒星喷流、流出、星周盘和磁场
DOI：
10.1093/mnras/stz740
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发表时间：
2019
影响因子：
4.8
通讯作者：
Masahiro N.
中科院分区：
文献类型：
--
作者：
Hirano;Shingo; Machida;Masahiro N.
最近的观测揭示了原恒星周围的各种现象，例如流出物和磁场之间的错位、喷流进动以及喷射团块的时间变化，这些现象的起源尚有争议。我们对旋转轴相对于初始磁场倾斜 45° 的恒星形成核心中的原恒星形成进行了三维电阻磁流体动力学模拟，其中原恒星的空间分辨率为 0.01 au。在低密度的外部区域，由于通量冻结，星前核心沿着磁场线收缩。另一方面，在高密度内部区域，当气体数密度超过约时，磁耗散变得有效并减弱磁效应。然后，压平圆盘的法线方向与角动量矢量对齐。流出、射流和原恒星喷射是由星周盘的不同尺度驱动的，并且在垂直于扭曲盘的不同方向上喷流。这些轴与全局磁场方向不一致，并且随时间变化。这项研究表明，只有假设恒星形成核心围绕与磁场不同的方向旋转，才能同时再现观测报告的几种错位性质。
Recent observations uncover various phenomena around the protostar such as misalignment between the outflow and magnetic field, precession of the jet, and time variability of the ejected clumps, whose origins are under debate. We perform a three-dimensional resistive magnetohydrodynamics simulation of the protostar formation in a star-forming core whose rotation axis is tilted at an angle 45° with respect to the initial magnetic field, in which the protostar is resolved with a spatial resolution of 0.01 au. In low-dense outer region, the prestellar core contracts along the magnetic field lines due to the flux freezing. In high-dense inner region, on the other hand, the magnetic dissipation becomes efficient and weakens the magnetic effects when the gas number density exceeds about. Then, the normal direction of the flattened disc is aligned with the angular momentum vector. The outflow, jet, and protostellar ejection are driven from different scales of the circumstellar disc and spout in different directions normal to the warped disc. These axes do not coincide with the global magnetic field direction and vary with time. This study demonstrates that a couple of misalignment natures reported by observations can be simultaneously reproduced only by assuming the star-forming core rotating around a different direction from the magnetic field.