Modern view of the warm ionized medium
  We review the observational evidence that the warm ionized medium (WIM) is a
major and physically distinct component of the Galactic interstellar medium.
Although up to ~20% of the faint, high-latitude H-alpha emission in the Milky
Way may be scattered light emitted in midplane H II regions, recent scattered
light models do not effectively challenge the well-established properties of
the WIM.
