Radiative Acceleration of Coronal Gas in Seyfert Nuclei
  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. 
L. Binette