A new state composed of quasiperiodic traveling waves has been observed in very close vicinity of the convection onset along a stable branch. This state precedes the recently discovered confined traveling-wave state, and consists of left- and right-going traveling waves which periodically alternate between either side of the cell. A time-dependent wave-number spectrum is a characteristic feature of this pattern. Effects of pattern translation and modulational instability can qualitatively explain the observed dynamical behavior.

• Received 10 February 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.838