Published in "The Interstellar Medium in Galaxies", eds. H.A. Thronson, Jr. and J. Michael Shull, 1990 Kluwer Academic Publishers.

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THERMAL PHASES OF THE INTERSTELLAR MEDIUM IN GALAXIES

Mitchell C. Begelman


Joint Institute for Laboratory Astrophysics
University of Colorado and National Institute of Standards and Technology, Boulder, CO 80309-0440


Abstract. This review deals with the theory of multiphase media in astrophysical systems. I discuss the basic reasons for the existence of multiple thermal phases, and the fundamental connection between multiphase media and thermal instability. After describing important examples of multiphase media, I examine the interactions among phases, i.e., mass exchange driven by thermal conduction and hydrodynamic ablation. Mass exchange may compete with radiative heating and cooling for control of the thermal state of the hot phase, and may alter the thermal stability properties of the system.


Table of Contents

INTRODUCTION

THEORY OF MULTIPHASE MEDIA
Why thermal phases?
Connection with thermal instability
Examples of thermal phases

INTERACTIONS AMONG PHASES
Evaporation and condensation
Ablation

Consequences of Mass Exchange
Mass exchange vs. radiative heating/cooling
Evolution of multiphase systems

CONCLUSIONS

REFERENCES

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