I review recent results derived from numerical simulations of the turbulent
interstellar medium (ISM), in particular concerning the nature and formation of
turbulent clouds, methods for comparing the structure in simulations and
observations, and the effects of projection of three-dimensional structures
onto two dimensions. Clouds formed as turbulent density fluctuations are
probably not confined by thermal pressure, but rather their morphology may be
determined by the large-scale velocity field. Also, they may have shorter
lifetimes than normally believed, as the large-scale turbulent modes have
larger associated velocities than the clouds' internal velocity dispersions.
Structural characterization algorithms have started to distinguish the best
fitting simulations to a particular observation, and have opened several new
questions, such as the nature of the observed line width-size relation and of
the relation between the structures seen in channel maps and the true spatial
distribution of the density and velocity fields. The velocity field apparently
dominates the morphology seen in intensity channel maps, at least in cases when
the density field exhibits power spectra steep enough. Furthermore, the
selection of scattered fluid parcels along the line of sight (LOS) by their
LOS-velocity inherent to the construction of spectroscopic data may introduce
spurious small-scale structure in high spectral resolution channel maps.Comment: 15 pages, no figures. To appear in the Proceedings of "The Chaotic
Universe", Roma/Pescara, Italy, 1-5 Feb. 1999, eds. V. Gurzadyan and L.
Bertone. Uses included .cls fil
