The periodic nature of this mode can be seen in the rhythmic nature of the expansions and contractions. The nonperiodic nature of the mode manifests itself by the varying position and the changing number of bright regions that appear on successive expansions. The power spectrum of this mode shows both sharp peaks due to the radial pulsation as well a broad background due to the chaotic motion of the cells .
At larger values of the flow rate a 9/1 ordered state of cellular flames is observed with no pulsations. At lower values of the flow rate, the cellular structure is not present, and the flat flame front pulsates in the radial mode in which it periodically and uniformly changes its radial extent. At still lower values the flame front extinguishes. The occurrence of these states with increasing flow rate is shown in Figure 6 a-c. A steady flame front is not observed at equivalence ratios exhibiting the pulsating-cellular interaction.