Propagation and Morphology of Pressure-Confined Supersonic Jets

Abstract

The beautiful, high resolution radio maps of jets, lobes, and hot-spots coming off the VLA challenge theorists to explain these phenomena in terms of simple, well-understood physical laws. The difficulty is often not one of finding a reasonable set of physical laws, but of finding their solutions. Analytic solutions of jet structure are limited to steady, isentropic, 1-dimensional flow in channels of slowly-varying cross section; analytic studies of jet stability are limited to modes of small amplitude which, in this regime, assume equal importance as well as unimportance for the gross structure of the flow. Numerical simulation provides a means for investigating those time-dependent, multidimensional, nonlinear solutions that are beyond the reach of analytic tools — solutions that must be relevant to an understanding of astrophysical jets. In an age when computing hardware and software are advancing so rapidly compared to analytic techniques, it is natural to turn to the computer for answers, approximate though they may be.