Dynamical Aspects of Spatiotemporal Chaos at the Onset of Electroconvection in Homeotropic Nematics

The systematic experimental study of direct transition “nonconvective state — spatiotemporal chaos” in electrohydrodynamic convection of a homeotropically aligned nematic is carried out. The transient patterns, both below and beyond the Lifshitz point, are studied and classified. The patterns initially correspond to oblique and normal rolls, respectively. In all the cases the transition to chaos undergoes slow spatiotemporal modulations of the local roll orientation. This results in the final dynamical patterns isotropic on large spatial scales. The dynamics of the final patterns are also studied with a quantitative analysis of the power spectra of turbulent modes and their autocorrelation functions. The exponential decay of the correlations in time is proved.