Three-dimensional radiative instabilities in a stratified plane jet

We investigate the three-dimensional stability of a stratified plane Bickley jet in the Boussinesq approximation framework. The angle $\theta$ between the shear plane and the direction of stratification and the Froud number $Fr$ are considered as a control parameters. Following the parallel flow approximation, the instability wave solution is sought in the form of a normal mode in two directions. We draw attention to a mechanism whereby Kelvin-Helmholtz mode may have a radiative structure and more generally how internal waves (or gravity waves) associated with unstable radiative modes may be spontaneously generated.