Statistical closure approximations and the fluctuation-dissipation theorem for drift-wave interaction

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Abstract
The statistical dynamics of a truncated (three-wave) model for drift-wave interaction are studied using numerical simulation in order to determine appropriate turbulence modeling approaches. The nonlinear dynamical equation is integrated for a Gaussian ensemble of initial states, and time-lag correlation functions and infinitesimal response functions are computed. The fluctuation-dissipation relation, an assumption of many statistical closure approximations, is shown to be qualitatively valid for statistical steady states of the system. Guided by the ensemble results, a Markovian turbulence model is selected and investigated.