Collapse and Fragmentation of Magnetic Molecular Cloud Cores

通过计算模型分析了磁化分子云核坍缩和碎裂形成星星的初始阶段，其中包括磁场和辐射传输的影响。观测表明，磁场对分子云复合物的动力学是重要的。目标是将更详细的磁场物理学整合到模拟中，以更好地理解致密分子云核心的碎裂以及双星和多星星系统的起源。磁场相互作用的重要影响可以通过在状态方程中包括额外的项或通过修改重力项来近似处理。在此之前，研究人员在他的代码中实现了磁场效应，将其视为标量压力项，通过重力稀释（代表磁场线张力），通过磁制动近似，以及通过磁场双极扩散的压力支持损失的参数化。在这里，这些以前的近似在主要研究者的代码被替换为一个简化的磁流体动力学（MHD）的例行程序，其中包括一个数值解的磁感应方程，和适当的治疗双极扩散。从更新的代码的结果进行比较，以前的伪磁计算，并从芝加哥大学的FLASH自适应网格细化代码的结果。这些比较应该提供关于不同计算方法的鲁棒性或弱点的良好见解，以模拟云核碎裂和崩溃期间磁场相互作用的物理学。

The initial stages of star formation through collapse and fragmentation of magnetized molecular cloud cores are analyzed by computational models which include the effects of magnetic fields and radiative transfer. Observations show that magnetic fields are important for the dynamics of molecular cloud complexes. The goal is to integrate more detailed physics of magnetic fields into the simulations to better understand the fragmentation of dense molecular cloud cores and the origin of binary and multiple star systems.The important effects of magnetic field interactions can be treated approximately by including extra terms in the equation of state or by modifying gravity terms. Previously the investigator had implemented the magnetic field effects in his code by treating it as a scalar pressure term, by the dilution of gravity (representing magnetic field line tension), by a magnetic braking approximation, and by parameterizations of the loss of pressure support through ambipolar diffusion of magnetic fields. Here these previous approximations in the principal investigator's code are replaced with a simplified magnetohydrodynamics (MHD) routine that includes a numerical solution of the magnetic induction equation, and proper treatment of ambipolar diffusion. The results from the updated code are compared to the previous pseudo-magnetic calculations, and to results from the University of Chicago's FLASH adaptive mesh refinement code. The comparisons should provide good insights about the robustness or weaknesses of the different computational approaches to model the physics of magnetic field interactions during cloud core fragmentation and collapse.