Numerical Study on Evolution from Magnetized Cloud to Protostar Using Three-Dimensional Nested Grid Method

三维嵌套网格法从磁化云到原恒星演化的数值研究

基本信息

批准号：
14540233
负责人：
TOMISAKA Kohji
金额：
$ 1.92万
依托单位：
National Astronomical Observatory of Japan
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

Using three-dimensional magnetohydrodynamical (NM) simulations, the contraction of the interstellar loud and star formation are studied for the density range from 102 to 1012 cm3.1. In the nested grid method, a number of grid systems are used. Fine grids cover the high-density center while coarse grids cover the low-density envelope, which guarantees the numerical accuracy in the simulation of self-gravitational collapse. MHD simulation programs (2-dimensional and 3-dimensional) based on the nested grid method was developed, in which the Poisson equation of the self gravity is solved with a multigrid iteration method modified for the nested grid.2. Axisymmetric 2D simulations show that a disk extending perpendicular to the magnetic field is made and that after the adiabatic core forms at the center with a density of〜10^10 cm-3 gas is ejected perpendicular to the disk owing to the angular momentum transport from the core to the flow.3. Three-dimensional MHD simulations found three diffe … More rent evolutions for the adiabatic core which will form new-born stars.(1) Spiral density wave develops in the adiabatic core. High-density (at least two) parts of the arms contract and form binary protostars (spiral fragmentation).(2) In the isothermal disk, nonaxisymmetric perturbations grow and form bar structure. High-density parts of the bar-shaped adiabatic core collapse by the self-gravity and binary protostars form in the bar (bar fragmentation).(3) The adiabatic core never fragment and a centrally-peaked core continues to contract and form a single protostar (nofragmentation).4. Condition for fragmentation is obtained as the ratio of the angular rotation speed to the magnetic flux density is larger than 3 times 10-7 y-1 micro G-1.5. Even if the initial rotation vector is not parallel to the magnetic field, magnetic field and rotation vector becomes to be aligned each other near the center of the cloud in the course of contraction. A disk runs in the perpendicular direction to the local magnetic field. Less

使用三维磁性磁性（NM）模拟，研究了星际大声和恒星形成的收缩，密度范围为102至1012 cm3.1。在嵌套网格方法中，使用了许多网格系统。细网格覆盖了高密度中心，而粗网格覆盖了低密度包膜，这可以保证在模拟自我崩溃的模拟中的数值准确性。开发了基于嵌套网格方法的MHD仿真程序（二维和三维），其中使用为嵌套网格修改的多移民迭代方法来求解自重力的泊松方程。2。轴对称2D模拟表明，制造了垂直于磁场的磁盘，并且在中心的绝热核心形成后，密度约为10^10 cm-3气体被弹出垂直于圆盘的驱射到磁盘上，这是由于核心动量从核心转运到流动流到流量的3。三维MHD模拟发现了三个差异……对绝热核心的更多租赁演变将形成新生的恒星。（1）螺旋密度波在绝热核心中发展。武器合同的高密度（至少两个）部分并形成二元质恒定（螺旋碎片）。（2）在等热盘中，非轴抗扰动生长并形成条形结构。条形的绝热核心的高密度部分是通过杆中的自我强度和二进制质恒定的形式（条形碎片化）。（3）绝热核心永不碎片，中央峰的核心继续收缩并形成单个质体（非碎片化）.4。由于角度旋转速度与磁通量密度的比率大于3倍10-7 Y-1 Micro G-1.5，因此获得了碎片的条件。即使初始旋转矢量与磁场不平行，在合同过程中，磁场和旋转向量也会在云的中心附近相互对齐。磁盘沿垂直方向向局部磁场运行。较少的