ON THE NONLINEAR MECHANICS OF MAGNETOHYDRODYNAMIC STABILITY

The nonlinear stability of magnetized plane Poiseuille flow, the magne tized plane jet, and the plane current-vortex sheet is examined. If it is assumed that the perturbation retains the form of the linearly uns table eigenmode, and that the most significant nonlinear effect is the distortion of the mean flow and magnetic field, then a Landau nonline ar stability equation can be derived from the streamwise-averaged pert urbation energy balance. Secondary equilibrium velocity and magnetic f ields are predicted. The possibility of subcritical instabilities also is discussed.