  The line ratios from coronal gas in Seyferts can be successfully fitted with
photoionized clouds of high densities and low volume filling factor. The
ionization parameter implied is sufficiently high that models must consider the
effect of radiation pressure from the active nucleus. In spite of the nucleus
gravitational force, radiation pressure is sufficiently strong to compress and
radially accelerate the internally stratified gas clouds provided these contain
small amounts of dust (~10% of solar neighborhood value). This radial
acceleration could explain the blueshift of the coronal lines relative to
systemic velocity without the need of invoking an ambient `pushing' wind.
Embedded dust has the interesting effect of making the photoionized clouds
marginally ionization bounded instead of matter bounded.
