Defect chaos in a convective system limited by domain walls

The transition to turbulence in an electroconvective system of nematics separated by domain walls of the in-plane director is studied by observing the temporal change in image intensity. The measured time series are analyzed by the sonogram method. In the system where the domain structure is formed by abnormal roll instability, defect chaos appears as intermittent periodic oscillation limited by the domain walls. By increasing applied voltage, a periodic defect lattice appears. In the higher voltage region, the defect lattice collapses and changes into local turbulent states. The spatiotemporal intermittency is observed through these local turbulent domain motions.