Angular momentum transport associated with finite plasma temperature in accreting disks

A "hot" plasma mode that can be excited in a rotating Keplerian disk imbedded in a magnetic field with a significant toroidal component, is found analytically. This mode is shown to transport angular momentum outward, that is the primary requirement for the occurrence of mass accretion on the central object. The relevant distinctive feature is that the mode depends on the effects of the finite plasma compressibility and finite anisotropic ion longitudinal (relative to the field) viscosity and sound velocity; the driving factor of the relevant instability being the combination of the finite plasma temperature and the (negative) radial gradient of the rotation frequency. Electrostatic velocity gradient driven modes, in a plasma column with an axial magnetic field, that depend on the effects of a longitudinal viscosity or a viscous-like term, finite electron temperature and compressibility have been similarly predicted earlier and one of them has been experimentally confirmed recently by other authors. (C) 1997 Published by Elsevier Science B.V.