Kinematics and Dynamics of Diffuse Astrophysical Media

The area of diffuse astrophysical media is enormous and ranges over circum­ stellar to extragalactic scales. The physical conditions can vary from cool dusty gases to collections of relativistic particles. Flows in such media are set up by en­ ergy and momentum injection from winds, jets and explosions. The study of these phenomena involves physics, chemistry and, inevitably, hydrodynamics. One of the most important aspects of this study is the ever increasing overlap between theory and observation. Indeed, it can be argued that the only way to really understand these complex flows which can never be duplicated under terrestrial conditions, is to encourage this overlap, and this was one major aim of this Conference. Because of the long theoretical and observational association of the Manchester Group with this general area, Manchester seemed an appropriate venue for this Con­ ference. But in fact this long association and the actual year of the Conference are connected. In 1951 Franz Kahn joined the Astronomy Department at Manchester University and immediately the study of diffuse media, particularly the hydrody­ namic aspects, commenced and has flourished ever since. Franz became Head of the Astronomy Department in 1981 following the retirement of Professor Z. Kopal, who founded the Department and was instrumental in attracting Franz to it. In 1993, Franz retired from this position and a most serendipidous coincidence was his election to the Royal Society announced shortly before the Conference.