An adaptive mesh magneto-hydrodynamic analysis of interstellar clouds.

Interstellar clouds play a key role in many astrophysical events. The interactions of dense interstellar clouds with shock waves and interstellar wind were investigated using an adaptive three-dimensional Cartesian mesh approach to the magneto-hydrodynamic equations. The mixing of the cloud material with the post-shock material results in complex layers of current density. In both the shock and wind interactions, a tail develops similar to the tail found with comets due to the solar wind. The orientation of this tail structure changes with the direction of the magnetic field, and may be useful to observationally determining the orientation of magnetic fields in the interstellar medium. The octree data structure was analyzed in regard to parallel work units. Larger block sizes have a higher volume to surface ratio and support a higher percentage of computational cells to non-computational cells, but require more cells at the finest grid resolution. Keeping the minimum resolution of the grid fixed, and averaging over all possible grids, the analysis confirms experience that block sizes larger than 8 x 8 x 8 cells do not improve storage efficiency. A novel algorithm was developed to implement rotationally periodic boundary conditions on quadtree and octree data, structures. Astrophysical flows with symmetric circulation, such as accretion disks, or periodic instabilities, such supernova remnants, may be able to take advantage of such boundary conditions while maintaining the other benefits of a Cartesian grid.Ph.D.AstronomyPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126744/2/3276211.pd