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Article Contents

ABSTRACT

1.INTRODUCTION

2.VIEW FROM THE INSIDE: DIVING INTO THE PHYSICS OF THE WARM IONIZED MEDIUM IN OUR GALAXY
2.1.Basic characteristics of the WIM and diagnostic tools
2.2.Ionization state
2.3.Temperature
2.3.1.[N II], [S II] and [O II] with respect to Halpha
2.3.2.[N II] l5755 / [N II] lambda6583
2.3.3.Line widths
2.4.Warm ionized and neutral gas
2.5.The role of superbubbles

3.VIEWS FROM THE OUTSIDE: DIFFUSE IONIZED GAS AND STAR FORMATION RATES IN EDGE-ON GALAXIES
3.1.Diffuse ionized gas in the halo and star formation in the disk
3.2.The disk-halo connection and hot gas

4.VIEWS FROM THE OUTSIDE: THE SOURCE OF THE DIFFUSE IONIZED GAS IN FACE-ON GALAXIES
4.1.Radiation from O stars and the surface brightness of the DIG
4.2.An escape model for Lyman continuum propagation
4.3.Line ratio studies

5.MODELING THE WIM/DIG: EFFECTS OF RADIATION TRANSFER THROUGH A CLUMPY INTERSTELLAR MEDIUM
5.1.What exactly is an H ii region?
5.2.Modeling the ionization structure of the DIG
5.2.1.Escape of ionizing radiation through superbubbles
5.2.2.Two- and three-dimensional ionization structure of the DIG
5.3.Modeling the emission line spectrum of diffuse ionized gas
5.3.1.One-dimensional models
5.3.2.Two- and three-dimensional models
5.3.3.Interfaces and three-dimentional H ii regions
5.3.4.Leaky H ii regions and the He+/H+ problem

6.IONIZING RADIATION FROM HOT GAS-COOL GAS INTERFACES
6.1.Types of interfaces
6.2.A test case

7.SOME QUESTIONS FOR FUTURE STUDY
7.1.What is the source of the elevated temeratures?
7.2.What is the spatial distribution of the gas?
7.3.How much ionizing radiation escapes the galaxy?
7.4.Do hot, pre-white dwarf stars play a role?
7.5.Is missing atomic data important?
7.6.What insights will new global models provide?

A LIST OF ACRONYMS AND TERMS

REFERENCES