Theoretical Study of Time Dependent Radiative Transfer in Relativistic Astrophysical Plasmas

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I investigated the properties of relativistic plasmas which are produced near massive black holes in quasars and active galactic nuclei. I developed the numerical code which treats time dependent radiative transfer with Compton scattering and electron-positron pair production. I studied the time development of the instantaneously heated plasmas and found that the initial thermal energy of protons is transferred to electrons and photons on the time scale of about 10 times the initial Thomson time and about 20 percent of it is used for pair production. I also studied the stationary structure of plasma clouds and obtained the spatial distribution of proton and electron temperatures, pair concentration and photon spectra. In the central region the temperatures are lower and the pair concentration is higher than the uniform model predicts for the same heating rate. Pair atmosphere is less de veloped because of the anisotropic distribution of photons.The results are applied to the two-temperature accretion disks, taking account of the effects of electron-positron pairs. I found that stationary solutions are not realized for high accretion rates because pair equilibrium is not established for the expected range of electron temperature and Thomson depth. The critical accretion rate corresponds to only a few percent of the Eddington luminosity when either bremsstrahlung or the Comptonization of cyclotron higher harmonics dominates the radiation process.This result raises the problem of the behavior of the two-temperature accretion disks for high accretion rates. I examined one possibility of hydrodynamical wind blowing from hot disks in a simplified way and dound that a significant matter can be lost through the wind. A fuller investigation will be continued.