Destabilizing effect of shear flow — beyond Kelvin-Helmholtz instability

Abstract

Recent progress in linear spectral studies of incompressible plasma (fluid) with flows is reviewed. Mathematically, non-Hermiticity of the generating operator brings about incompleteness of the eigenvalue analysis and unremovable coupling between modes. This may lead to secular growth (algebraic in time) even if all eigenvalues exhibit stable oscillations. Physically, the stretching effect of shear flow is considered a stabilizing mechanism for various plasma instabilities; however, shear flow may equally effectively destabilize a class of plasma modes. The condition for stabilization/ destabilization is discussed as well as its physical mechanisms.