Jets and disks around young stars

Equilibrium models are constructed for quasi-Keplerian pressure-confined ga s disks with a constant half-thickness-to-radius ratio, in the gravitationa l field of a central massive object (young star). It is shown that the equi librium parameters of such disks are uniquely determined by the physical pa rameters of the surrounding atmosphere. A linear analysis is performed for the stability of a model with a gas disk in an atmosphere and bipolar jets perpendicular to the plane of the accretion disk. The possible development of a discrete set of unstable acoustic and gradient wave modes in such syst ems is shown. The existence in the accretion-jet system of unstable axisymm etric perturbations that form radiating knots in the jets may lead to synch ronization of these knots in the two oppositely directed jets, and to the e fficient outward transport of the angular momentum of the accretion-disk ma terial.