The galactic corona

Abstract

The IUE observations and theories involving the gaseous galactic corona of the Milky Way are reviewed. Observational topics emphasized include results relevant to the z distribution, kinematics, and ionic and elemental abundances of the gas. The theories for the support, ionization, and kinematics of the galactic halo appear to require a merging of the ideas associated with the galactic fountain models and the photoionized halo models. The Si IV found in the galactic halo is likely mostly produced by photoionization while the N V is probably mostly produced by collisional ionization in cooling fountain gas; C IV may represent an intermediate case with important contributions from photoionization and from collisional ionization.