The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
The observed properties of the diffuse ionized gas (DIG) in our Galaxy
are not easily reconcilable with simple photoionization models.
Photoionization models, however, can reproduce the observed properties
of H 
regions. This suggests that there are different or
additional physical processes at work in the DIG. We have developed a
model of the DIG whereby it is ionized by a relatively soft ionizing
spectrum 
and is also heated by an
additional thermal mechanism: the dissipation of turbulence. This
model predicts the same electron temperature, 
ratio,
ratio and 
ratio as observed in the DIG.
The model suggests that the observed 
emission from the diffuse
ISM does not originate from the oxygen in the DIG. Without the
turbulent thermal heating term, this model will not reproduce the
observed properties of the DIG. The dissipation of turbulence may
also be important in other phases of the ISM.