Accretion disks with a cloudy sky - Photon floater

Materials rotating above/below an accretion disk around a central object suffer from the influence of the strong radiation fields of the disk as well as the gravity of the central object. We find that there exists a critical floating height where the vertical gravity of the central object is balanced by the radiation force from the disk, and the materials are photon-floating there. The critical floating height is detemined by the disk effective luminosity Gamma(eff), which is defined by Gamma(eff) = (sigma/sigma(T))(m(p)/m)(L(d)/L(E)), where sigma and m are the material cross-section and mass, respectively, sigma(T) and m(p) the Thomson cross-section and the proton mass, respectively, and L(d) and L(E) the disk luminosity and the Eddington luminosity, respectively. For small Gamma(eff) or large tau(much greater than z) the critical floating height z(F) is expressed as z(F) similar to 3 r(in)Gamma(eff), where r(in) is the inner radius of the disk. The astrophysically important point is that this critical floating height is dynamically stable; hence, materials, such as gas clouds or dust or artificials, suffering from the radiation field of the disk drift toward this floating height. Such floating clouds - photon floaters - above/below the disk partially occults the disk. If the disk sky is cloudy, the observed luminosity becomes irregular. Futhermore, if a cloudy sky is present, the emitted spectrum would be remarkably modified due to reprocessing. A cloudy sky would also produce absorption/emission features. In addition, since the radiation from the disk is scattered by floating clouds at a critical floating height, the disk appears as if its thickness had become z(F). The weather environment, such as a cloudy or dusty sky, changes the disk appearance significantly.