THERMAL CONDUCTION IN ACCRETION DISK CORONAE

We study the effects of thermal conduction in a hot, active corona abo ve an accretion disk. We assume that all of the dissipative heating ta kes place in the corona. We find that the importance of conduction dec reases with increases in the local dissipative compactness of the coro na, l(diss,loc), and increases with increasing abundance of electron-p ositron pairs. For l(diss,loc) < 1, a significant fraction of the ener gy released in the corona may be carried away by the conductive flux, leading to formation of a relatively hot transition layer below the ba se of the corona. Comptonization of disk radiation in such a layer may account for the presence of soft X-ray excesses in the spectra emitte d by disk-corona systems.