Fragmentation of a Filamentary Cloud Threaded by Perpendicular Magnetic Field
Fragmentation of a Filamentary Cloud Threaded by Perpendicular Magnetic Field
复制标题
垂直磁场穿过的丝状云的破碎
DOI：
10.1017/s1743921319003600
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Tomisaka Kohji
中科院分区：
文献类型：
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作者：
Hanawa Tomoyuki;Kudoh Takahiro;Tomisaka Kohji
丝状的分子云被认为是分裂成团块和核心。然而，如果磁场垂直于云的轴，则可以通过磁力抑制碎裂。我们使用一个简单的模型来评估效果。我们的模型云被假定为具有类似于Plummer的径向密度分布，其中r和H分别表示到云轴的径向距离和尺度长度。符号ρc和p分别表示轴向密度和径向密度指数。初始磁场被假定为均匀的并且垂直于云轴。模型云被假定为由气体压力和湍流支撑以抵抗自身重力。根据Hanawa，Kudoh和Tomisaka（2017）的方法，我们已经获得了碎裂不稳定性的增长率作为波长的函数。不稳定性主要取决于外边界。如果位移在离云轴很远的区域消失，则云的碎裂被中等磁场抑制。如果在离云很远的区域，沿着磁场的位移是沿着恒定的，那么即使磁场无限强，云也是不稳定的。折射率p越小，最不稳定模式的波长越长。
Filamentary molecular clouds are thought to fragment to form clumps and cores. However, the fragmentation may be suppressed by magnetic force if the magnetic fields run perpendicularly to the cloud axis. We evaluate the effect using a simple model. Our model cloud is assumed to have a Plummer like radial density distribution, , where r and H denote the radial distance from the cloud axis and the scale length, respectively. The symbols, ρc and p denote the density on the axis and radial density index, respectively. The initial magnetic field is assumed to be uniform and perpendicular to the cloud axis. The model cloud is assumed to be supported against the self gravity by gas pressure and turbulence. We have obtained the growth rate of the fragmentation instability as a function of the wavelength, according to the method of Hanawa, Kudoh & Tomisaka (2017). The instability depends crucially on the outer boundary. If the displacement vanishes in regions very far from the cloud axis, cloud fragmentation is suppressed by a moderate magnetic field. If the displacement is constant along the magnetic field in regions very far from the cloud, the cloud is unstable even when the magnetic field is infinitely strong. The wavelength of the most unstable mode is longer for smaller index, p.