1999ApJ...518..814M

We develop a method for investigating waves and instabilities in astrophysical shear flows with complex kinematics. Using new tools, we find an unexpected richness in the spectrum of compressible fluctuations sustained by such a flow. The principal characteristic of the revealed exotic phenomena is their asymptotic persistence in the absence of viscosity. ``Echoing'' as well as strongly unstable (including parametrically driven) solutions are identified. Examples of astrophysical shear flows with nontrivial velocity structure where these method and results can be applied are also discussed.