GRAVITY MODE-INSTABILITIES IN DIFFERENTIALLY ROTATING-DISKS

The modal structure of internal gravity modes in shearing systems is investigated using analytical methods. If the buoyancy frequency profile satisfies certain symmetry conditions, two types of instabilities are found - one of which can be explained by over-reflection, the other by mode resonances. Due to the intrinsically low pattern speed of gravity waves, the shear-driven instabilities occur predominantly at low shear rates. Their importance for accretion flows and differentially rotating stars is stressed. © 1990 Oxford University Press. All rights reserved.