SHEAR-FLOW GENERATION BY DRIFT ROSSBY WAVES

The generation of shear flow driven by a large amplitude drift wave, r epresented by the Hasegawa-Mima-Charney (HMC) equation, has been inves tigated. It is shown that, besides a finite amplitude threshold for th e shear flow instability to occur, there is also a necessary condition on the aspect ratio of the large amplitude drift wave, due to conserv ation of the average potential vorticity, that needs to be satisfied. A comprehensive comparison of the shear-flow instability criterion for the HMC equation and the incompressible, invisicid, hydrodynamic equa tion has been undertaken. (C) 1995 American Institute of Physics.