Multiple transitions in rotating turbulent Rayleigh-B\`enard convection

etc15 Tracking Number 251

Sharp transitions between potentially different turbulent states are unexpected because one might think that they should be washed out by the prevailing intense fluctuations and short coherence lengths and times. Contrary to this expectation, we found a {\it sequence} of such transitions in turbulent rotating Rayleigh-B\'enard convection as the rotation rate was increased. This phenomenon became most prominent at very large Rayleigh numbers up to $2\times 10^{12}$ where the fluctuations are extremely vigorous. It was found in the heat transport as well as in the temperature gradient near the sample center. We conjecture that the transitions are between different large-scale structures which involve changes of symmetry and thus can not be gradual.