Models for X-ray Emission from Radio Quiet AGNs
  The current status of understanding of the X-ray emission from Seyfert galaxies involves thermal Comptonization of soft photons by mildrelativistic electrons and positrons. I review observational and theoretical arguments supporting such a view, discussing current models proposed for the structure of the innermost part of the accretion flow: extended coronae, small scale flaring blobs, advection dominated accretion disks and small scale cold cloudlets. 
Francesco Haardt