ECCENTRIC ACCRETION DISKS

We obtain evolutionary equations for non-stationary viscous accretion discs in which particles are orbiting along Keplerian ellipses that ar e slowly drifting towards the centre. It is shown that, for any reason able viscosity law, stationary accretion is possible, with ah orbiting particles moving with the same eccentricity. We investigate the stabi lity of circular discs with respect to eccentric particle motion and f ind that instability develops for some viscosity laws. In particular, we show that formal application of the alpha-prescription for the visc osity leads to instability.