Stochastic switching in a nonequilibrium crystal: a simple model for intermittent dynamics

Flow intermittency in the transition to turbulence is an important and long-standing problem in fluid mechanics. Nonlinear dynamics and geometric heterogeneity are known to strongly affect the patterns and range over which intermittency is observed. We have developed an experimental and numerical system which also displays stochastic, intermittent dynamics, and is sensitive to nonlinearities and heterogeneities. The experiments utilize dusty (complex) plasma, which consists of colloidal particles (dust) immersed in rarified charged gas (plasma) environment. Inertia is important: unlike colloidal suspensions that are characterized by overdamped dynamics, microparticles in plasma obey virtually underdamped dynamics. At low gas pressures, particles in a quasi-2D crystalline layer experience self-induced vertical vibrations that result in switching between crystalline and gas-like phases. The initiation of the gas-phase is due to an energy cascade from high-frequency modes to low-frequency modes in the system, leading to intermittent dynamics over a broad range of time scales. The dynamics can also be cast as two coupled ODEs for the kinetic energy in horizontal and vertical directions which resemble similar equations used to model the transition to turbulence.