SPATIOTEMPORAL INTERMITTENCY IN LINES OF VORTICES

The turbulent regimes of lines of electromagnetically forced vortices are investigated experimentally. It is found that turbulence appears i n the form of spatiotemporal intermittency. At lower values of the con trol parameter, a first regime is observed, characterized by spontaneo us 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. A t larger values of the control parameter the bursts connect and the sy stem percolates. In this second regime, the distributions of the lifet imes of the laminar domains are exponential. The corresponding transit ions appear to be of second order. A model of coupled oscillators, wit h coefficients measured experimentally, is shown to reproduce reasonab ly well the characteristics of the turbulent regime below the percolat ion threshold. In these experiments, percolation is found to be a usef ul 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.