Anomalous hydrodynamic fluctuations during the development of thermal convection (Q1108150)

The spectral functions of the fluctuations of the hydrodynamic variables in an inhomogeneously heated liquid in the region of Rayleigh numbers close to the threshold of convective stability have been calculated using the equations of the correlation theory of thermal fluctuations in non- equilibrium statistical systems. It is shown that anomalous fluctuations, which form the structure of the flow in the regions of supercritical values of the Rayleigh number are of an essentially non-equilibrium nature and are completely accounted for by the long wavelength part of the correlation functions. The results of the calculations are used to analyze the effect of large-scale fluctuations on the Rayleigh scattering of radiation. It is is shown that, in a region where thermal convection develops, they are responsible for a phenomenon which is analogous to the critical opalescence of light during equilibrium phase transitions of the second kind.