PHYSICAL CONSTRAINTS ON THE SIZES OF DENSE CLOUDS IN THE CENTRAL MAGNETOSPHERES OF ACTIVE GALACTIC NUCLEI

The range of microphysical and global dynamical time-scales in the cen tral regions of active galactic nuclei (AGN) is sufficiently wide to p ermit the existence of multiphase structure. In particular, very dense , cool clouds can coexist with a hot, magnetically dominated medium an d can thereby efficiently reprocess the continuum radiation generated in this primary source region. The strong dynamical forces in this cen tral magnetosphere can give rise to extremely small clouds. Microphysi cal processes then determine whether such clouds can indeed survive, i n spite of their extremely contrasting properties relative to the surr ounding environment, for long enough to produce potentially observable thermal reprocessing signatures. We examine specific physical constra ints on the thicknesses of such reprocessing clouds. Our results are p lotted to show the range of conditions that is representative of the c entral regions of AGN. We find a parameter subspace in the extreme hig h-density regime for which the effects of microphysical diffusion proc esses can be overcome and for which cool gas can maintain pressure equ ilibrium with the ambient magnetosphere.