PHASE DEFECTS AND SPATIOTEMPORAL DISORDER IN TRAVELING-WAVE CONVECTION PATTERNS

Spatiotemporal disorder is studied in traveling-wave convection in eth anol-water mixtures. Spectral measures of disorder, linear correlation functions, and mutual information are used to characterize the patter ns, and are found to give a weak indication of the level of disorder. The calculation of the complex order parameter for experimental patter ns is described. It is found that the ordering of the patterns is acco mpanied by a dramatic change in the topological structure of the order parameter. Specific arrangements of defects are found to be associate d with the elements of traveling-wave patterns, and the net charge and total number of defects is introduced as a measure of disorder in the patterns. The coarsening of the patterns is marked by an accumulation of net charge and a dramatic decrease in the number of defects. The p hysical significance of the defects is discussed, and it is shown that the phase velocity of the waves is lower in the vicinity of the defec ts. The defect-defect correlation functions are calculated for the con vection patterns. It is shown that the ordering of the patterns is clo sely related to the apparent defect-defect interactions.