Electron-Positron Pair Equilibrium in a Mildly Relativistic Plasma: Effects of the Comptonization of Soft Photons

Abstract

We investigate the equilibrium pair concentration in an optically thin mildly relativistic plasma when copious soft photons are supplied by thermal synchrotron radiation. The pair equilibrium condition restricts the attainable states of a hot plasma which is supposed to exist in active galactic nuclei. There exist the maximum values for the electron temperature, the Thomson scattering depth, the size of aplasma and the strength of magnetic fields. We show that magnetic fields strengthen these restrictions considerably through the synchrotron-Compton process. For a plasma of the electron temperature higher than 8 x 10 B K, the proton density of 10 11 cm3 and the magnetic field of 10 4 G, the maximum of the Thomson scattering depth is ~ 10 and luminosity is less than ~ lO 44 erg/ sec.