We present a laboratory study on the instability of internal wave attractors in a trapezoidal fluid domain filled with uniformly stratified fluid. Energy is injected into the system via standing-wave-type motion of a vertical wall. Attractors are found to be destroyed by parametric subharmonic instability via a triadic resonance which is shown to provide a very efficient energy pathway from lon...

In contrast to conventional expectations based on the stability of steady shear flows, elementary time-periodic stratified flows that are unstable at arbitrarily large Richardson numbers are presented here. The fundamental instability is a parametric one with twice the period of the basic state. This instability spontaneously generates local shears on buoyancy time scales near a specific angle ...

The order parameter model based on the parametric Ginzburg-Landau equation is used to describe high acceleration patterns in the vibrated layer of granular material. At large amplitude of driving both hexagons and interfaces emerge. Transverse instability, leading to the formation of ‘‘decorated’’ interfaces and labyrinthine patterns, is found. Additional subharmonic forcing leads to controlled...

Experiments and theory characterize a parametric decay instability between plasma drift waves when the nonlinear coupling is modified by an electrostatic barrier. Novel mode coupling terms representing enhanced dissipation and mode phase shifts are caused by chaotic separatrix crossings on the wave-ruffled separatrix. Experimental determination of these coupling terms is in broad agreement with...

Abstract. The parametric instability of upper hybrid wave decay into back scattered upper hybrid wave and lower hybrid wave is considered for conditions of inhomogeneous plasma of spherical tokamaks. The possibility of absolute instability is demonstrated and the corresponding threshold is determined. It is shown that the threshold power increases with pump frequency and electron temperature. T...

We report an experimental study on the effect of an external phase noise on the parametric amplification of surface waves. We observe that both the instability growth rate and the wave amplitude above the instability onset are decreased in the presence of noise. We show that all the results can be understood with a deterministic amplitude equation for the wave in which the effect of noise is ju...