Magnetohydrodynamical Problems in the Galaxy

[94-23187] Balbus这个提案描述了许多不同的项目，涉及银河系的磁流体动力学（MHD）研究，它们共同关注微分旋转和磁场。弱磁场对差分旋转气体的影响已被证明是轴对称扰动的局部不稳定性，这可以影响银河系的演化。这些项目是：(a)扩展和发展现有的欧拉有限差分MHD规范，使其包括多种流体和有限电阻率；(b)对银河系磁场的起源和演化进行数值研究，充分考虑到弱磁场不稳定性的存在；(c)银河晕的解析和数值研究，其局部稳定性及其与二维磁化风的关系；(d)发展了银河系旋臂区域内MHD流体的局部引力坍缩的解析形式和显式数值解。最后一个项目的动机是需要有一个定义良好的定量程序来确定束缚结构何时脱离背景星际气体流。

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.