Detection of wave coupling cascade in space plasmas

空间等离子体中波耦合级联的探测（DECODE）旨在首次回答空间湍流和天体物理等离子体中是否存在三波耦合过程这一长期存在的问题。该项目包括三个支柱：分析方法的开发，使用数值模拟的波耦合检测，以及使用航天器观测。首先，实现了一个高分辨率的双相干估计直接在波矢频域检测三波耦合，并对等离子体湍流的合成数据的方法进行了测试。其次，双相干估计被施加到等离子体湍流直接数值模拟使用混合等离子体代码AIKEF。第三，将该方法应用于磁层多尺度使命中四个航天器采集的近地太阳风行星际空间等离子体湍流观测数据。研究是与奥地利和日本合作进行的。该项目将揭示等离子体湍流的基本机制，并将增进我们对空间湍流过程和行星际和星际空间等天体物理等离子体的理解。

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.