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Phase coherence in the solar wind MHD waves : Geotail data analysis and numerical simulation studies

太阳风 MHD 波的相位相干性：Geotail 数据分析和数值模拟研究

基本信息

批准号：
15540428
负责人：
HADA Tohru
金额：
$ 2.37万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

By analyzing magnetic field data obtained by Geotail spacecraft, and also by performing numerical simulations of various systems modeling nonlinear coupling of MHD waves, we have made research on several issues related to the wave phases.1.We have developed a method to quantitatively evaluate the phase coherence among waves, by comparing structure functions of the original and its phase shuffled and phase correlated surrogates. Application of the method to Geotail magnetic field data revealed that the MHD waves in the foreshock is in fact phase correlated, and the correlation is stronger as the turbulence amplitude is increased. We have further identified the origin of the phase coherence by a method using the wavelet filtering technique.2.By numerical time integration of various systems which model the nonlinear coupling of MHD waves, such as the triplet model, multiply-coupled triplet model, the DNLS equation, and the Hall-MHD set of equations, we discussed the relationship between the phase coherence, nonlinear dispersion relations, and transfer of energy among the different waves (or eigenmodes). We showed that the phase coherence is self-generated as the energy is transferred between the waves, and the phenomena can be modeled by avalanches.3.By performing test particle simulations, we discussed diffusion and acceleration of energetic particles in the MHD turbulence with phase coherent structures. We argued the relationship between statistics of the particle transport and that of the field fluctuations.

通过对Geotail探测器获得的磁场数据的分析，以及对各种模拟磁流体波非线性耦合的系统进行数值模拟，研究了与波相位相关的几个问题：1.提出了一种通过比较原始磁流体及其相位重排和相位相关替代物的结构函数来定量评价波之间相位相干性的方法。将该方法应用于Geotail磁场数据表明，前震中的MHD波实际上是相位相关的，并且这种相关性随着湍流振幅的增加而增强。2.通过对MHD波非线性耦合的三重态模型、多重耦合三重态模型、DNLS方程和Hall-MHD方程组的数值积分，讨论了MHD波的相位相干性、非线性色散关系、非线性色散关系和非线性色散关系之间的关系，以及不同波（或本征模）之间的能量传递。通过实验粒子模拟，讨论了具有相位相干结构的MHD湍流中高能粒子的扩散和加速问题。讨论了粒子输运统计与场涨落统计之间的关系。