Breathing Life Into Dead-Zones

¹ University of California, Merced
² Queen Mary University of London
³ NORDITA

^a e-mail: oumurhan@ucmerced.edu

Abstract

The terrestrial planet formation regions of protoplanetary disks are generally sufficiently cold to be con- sidered non-magnetized and, consequently, dynamically inactive. However, recent investigations of these so-called “Dead-Zones” indicate the possibility that disks with strong mean radial temperature gradients can support instabilities associated with disk-normal gradients of the basic Keplerian shear profile. This process, known as the Goldreich-Schubert-Fricke (GSF) instability, is the instability of short radial wavelength inertial modes and depends wholly on the presence of vertical gradients of the mean Keplerian (zonal) flow. We report here high resolution fully nonlinear axisymmetric numerical studies of this instability and find a number of features including how, in the nonlinear saturated state, unstable discs become globally distorted, with strong vertical oscillations occurring at all radii due to local instability. We find that nonaxisymmetric numerical experiments are accompanied by significant amounts angular momentum transport (α ~ 0001). This instability should be operating in the Dead-Zones of protoplanetary disks at radii greater than 10-15 AU in minimum mass solar nebula models.