The Kelvin‐Helmholtz Instability in Compressible Plasmas with Magnetic Field Shear

We investigate the effect of compressibility and magnetic field shear on the Kelvin‐Helmholtz instability in compressible stratified plasmas. We obtain two main results. First, for sufficiently low velocities the compressibility stabilizes the unstable modes present in an incompressible model (called main modes). This represents an important difference with the case without magnetic field shear. Second, new unstable modes appear (called secondary) which owe their existence to compressive perturbations. The secondary modes (of compressive character) determine the stability for values of velocity of the unperturbed flow that correspond to stable primary modes. In these cases the compressive modes do not disappear and may have appreciable growth rates. Therefore, compressibility effects may be relevant when discussing the stability of problems with magnetic field shear. Diagrams of stability and growth rates are shown that allow an easy visualization of the stability properties of a configuration