STABLE WAVE-NUMBER KINKS IN PARAMETRICALLY EXCITED STANDING WAVES

The stability of parametrically excited standing waves in large aspect ratio systems is investigated for small driving. Their phase diffusion equation is derived. It is found that for small group velocity of the underlying travelling waves the Eckhaus stable band of wave numbers can split up into two subbands which are separated by a region of unstable wave numbers. This gives rise to solutions with stable wave number kinks which bridge the unstable regime between the subbands. The kinks are approximately described by a Ginzburg Landau equation for a conserved order parameter. For other parameter values the transition to an equivalent of the Benjamin Feir instability can be controlled by the driving amplitude. © 1990 The Japan Society of Applied Physics.