The mechanism of wave-turbulent instability in nonequilibrium systems

The phenomena of wave-turbulent instability in hydrodynamic systems was actively discussed last year. The mechanism of this instability is next. The nonequilibrium system is slightly below the threshold of small-scale turbulence appearance. It means that parameter, determining level of nonequilibrity (shear of mean flow or temperature gradient etc.), less that some critical value. Then a large-scale wave passes through the system and varies this parameter locally. In that area where the parameter becomes more than threshold, turbulence arises (turbulent spots). Turbulence and wave amplify each other, using energy of nonequilibrity. The authors investigate mechanism of wave-turbulent instability in the nonisothermic dissipative plasma with a kinetic beam of charged particles. When the gradient of the kinetic distribution function of beam (in v-space) exceeds the threshold, the Cherenkov instability takes place and small-scale Langmuir turbulence arises. At the initial moment, this gradient is slightly below its critical value, but when a large-scale ion-sound wave passes through the plasma, the gradient arises locally and the interaction between Langmuir turbulence and the ion-sound wave leads to the wave-turbulent instability