Study on nonlinear wave dynamics in the magnetosphere via computer experiments and plasma waveform analysis

本文利用GEOTAIL卫星获得的等离子体波形数据和粒子模型进行了计算机实验，研究了地球磁层的非线性波动动力学。对波形的分析使我们能够提取每一种现象所涉及的空间和时间非线性变化。特别是，在边界层（如磁重联区）观察到的电子模式的波形分析对于等离子体加热、加速和扰动的关联是重要的。本研究项目的目的是通过计算机实验和分析GEOTAIL的波形数据来解决这些微观非线性波动动力学问题。在对波形的统计研究中，我们采用了独特的方法，如模式识别和传统的傅立叶变换。研究了宽带静电噪声（BEN）、窄带静电噪声（NEN）、电子回旋多谐波（ECH）和调幅朗缪尔波的波形。通过对这些波形的分析和计算机实验相结合，我们研究了波动动力学中的微观非线性过程。特别是BEN的产生机制的发现在本课题的研究中具有重要意义。我们首次发现BEN是由束流-等离子体相互作用产生的静电孤立波（ESW）构成的。通过计算机实验，我们还揭示了ESW是由束流-等离子体不稳定性产生的BGK模式的非线性解。为了对电磁波波形进行统计分析，提出了一种基于位模式匹配的电磁波波形自动提取方法。我们可以澄清光波的传播与电子束的传播之间的关系，以及光波的宽度与局部德拜长度的关系。统计分析结果与本研究的计算机实验结果吻合较好。少

We have studied the nonlinear wave dynamics observed in the Earth's magnetosphere by using plasma waveform data obtained with the GEOTAIL spacecraft and by performing computer experiments with particle model. The analysis of waveforms enables us to extract the spatial as well as temporal nonlinear variation involved in each phenomenon. In particular, waveform analysis of electron modes observed at boundary layers such as the magnetic reconnection region is important in association of plasma heating, acceleration, and perturbation. The aim of this research project is to solve these microscopic nonlinear wave dynamics by performing computer experiments as well as analyzing the waveform data of GEOTAIL. We also utilized unique method in the statistical study of waveforms such as the pattern recognition as well as the conventional Fourier transformation. We paid our attention to the waveforms of broadband electrostatic noise (BEN), narrow band electrostatic noise (NEN), electron cyclotron … More harmonic waves (ECH), and amplitude modulated Langmuir waves. By combining the analysis of these waveform and computer experiments, we examined microscopic nonlinear processes in the wave dynamics.In particular, the discovery of the generation mechanism of BEN is very significant in the present research project. We, for the first time, found that BEN is made of electrostatic solitary waves (ESW) which are created by the beam-plasma interaction. By Performing computer experiments, we also revealed that ESW is a nonlinear solution of BGK mode generated by the beam-plasma instability. To statistically analyze ESW, we developed a new method using the bit-patter matching, and succeeded in extracting ESW waveforms automatically. We could clarify the relation between the propagation of ESW and that of electron beams, and the width of ESW and the local Debye length. The statistical analysis shows a good agreement with the results obtained in the computer experiments conducted in the present studies. Less