Spatiotemporal intermittency in lines of vortices

The turbulent regimes of lines of electromagnetically forced vortices are investigated experimentally. It is found that turbulence appears in the form of spatiotemporal intermittency. At lower values of the control parameter, a first regime is observed, characterized by spontaneous nucleation of the turbulent domains, and algebraic distributions of the lifetimes of the laminar domains. On the space-time diagrams, the bursts are associated with amplitude holes and rapid phase changes. At larger values of the control parameter the bursts connect and the system percolates. In this second regime, the distributions of the lifetimes of the laminar domains are exponential. The corresponding transitions appear to be of second order. A model of coupled oscillators, with coefficients measured experimentally, is shown to reproduce reasonably well the characteristics of the turbulent regime below the percolation threshold. In these experiments, percolation is found to be a useful concept for the description of turbulence, and the results suggest that nonadiabatic effects, such as the discrete nature of the system, play a role in the system.