Observations of the ISM describe a turbulent, chaotic medium with large variations in flow velocity, density, temperature, and magnetic field strength over various scale lengths. Differences in gas characteristics give rise to regions where instabilities can occur. In particular, instabilities arise at the interfaces between different phases of the ISM, (i.e. molecular clouds, HI regions, or HII regions). This makes these interfaces promising sites for the formation of large structures in the ISM. Another possibility is the creation of compressed regions in which gravitational collapse may be initiated. Types of instabilities include Rayleigh-Taylor, Kelvin-Helmholtz, thermal, and a newly discovered instability driven by self gravity. The behavior and growth of each instability must be examined, not just individually, but also when coupled with the others. For instance, although a region may appear stable when instabilities are considered separately, the coupling of the dynamics and thermodynamics may give rise to a new instability with a significant growth rate for wavelengths of about a parsec. Analytical models have been done to study the linear growth of instabilities for idealized cases. I present the preliminary results of computational models following the nonlinear growth of coupled instabilities for various types of interfaces. The growth of the instabilities are seen to lead to structures and compressed regions consistent with observations. This work is supported by a Pre-Doc fellowship grant from the Florida Space Grant Consortium.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1999