Stable, unstable, and defected confined states of traveling-wave convection.

Abstract

I describe an extensive experimental study of the structure, propagation, and stability of one-dimensional confined states of traveling-wave convection in ethanol-water mixtures in an annular convection cell. The widths of these confined states are found to form a discrete set in parameter space. The principal difference between wide and narrow confined states lies in their dynamical stability: wide confined states are unstable for \ensuremath{\psi}\ensuremath{\gtrsim}-0.13 and can only be maintained in a steady state using active servo control, whereas narrow ``pulses'' are stable for all separation ratios studied. These observations are in qualitative agreement with the predictions of a complex-Ginzburg-Landau-equation model and in disagreement with previous observations of a continuum of confined-state widths at separation ratio \ensuremath{\psi}=-0.25. These experiments also document new confined states, including one in which lines of spatiotemporal dislocations separate slow and fast traveling waves.