Detection of wave coupling cascade in space plasmas

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DECODE (Detection of wave coupling cascade in space plasmas) aims for the first time to answer the long-standing question if a three-wave coupling process exists in turbulence in space and astrophysical plasmas. The project cosists of three pillars: development of an analysis method, wave coupling detection using numerical simulations, and that using spacecraft observations. First, a high-resolution bicoherence estimator is implemented to detect three-wave couplings directly in the wavevector-frequency domain, and the method is tested against synthetic data for plasma turbulence. Second, the bicoherence estimator is applied to plasma turbulence generated by direct numerical simulations using a hybrid plasma code AIKEF. Third, the estimator is applied to observational data of plasma turbulence interplanetary space sampled by four spacecraft of the Magnetospheric Multi-Scale mission in near-Earth solar wind. Research is conducted as an international collaboration with Austrian and Japan. The project will reveal the fundamental mechanism operating in plasma turbulence, and will advance our understanding of turbulent processes in space and astrophysical plasmas such as in interplanetary and interstellear space.