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.
