Magnetohydrodynamical Problems in the Galaxy

94-23187 Balbus 该提案介绍了一些涉及银河系磁流体动力学研究的不同项目，这些项目共同关注差异旋转和磁场。 弱磁场对差动旋转气体的影响已被证明是对轴对称扰动的局部不稳定性，这可能影响银河系的演化。 这些项目是：（a）扩展和发展现有的欧拉有限差分MHD代码，使之包括多种流体和有限电阻率;（B）对银河磁场的起源和演变进行数值研究，充分考虑到弱场不稳定性的存在;（c）对银河晕、其局部稳定性及其与二维磁化风的关系进行分析和数值研究;（d）发展了银河系旋臂区MHD流体局部引力坍缩的解析形式和显式数值解。 这最后一个项目的动机是需要有一个明确的和定量的程序，以建立当绑定结构退出背景星际气体流。

94-23187 Balbus This proposal describes a number of different projects involving magnetohydrodynamical (MHD) studies of the Galaxy, having in common a concern with differential rotation and magnetic field. The effect of a weak magnetic field upon differentially rotating gas has been shown to be a local instability to axisymmetric disturbances, which can influence Galactic evolution. The projects are: (a) the extension and development of an existing Eulerian finite difference MHD code to include multiple fluids and finite resistivity; (b) a numerical investigation of the origin and evolution of the Galactic magnetic field, taking fully into account the presence of the weak field instability; (c) analytic and numerical studies of the Galactic halo, its local stability properties, and its relation to a two-dimensional magnetized wind; and (d) the development of an analytic formalism for, and explicit numerical solutions of the local gravitational collapse of an MHD fluid in the spiral arm regions of the Galaxy. This last project is motivated by the need to have a well-defined and quantitative procedure for establishing when bound structure drops out of the background interstellar gas flow.