STUDY ON FORMATION PROCESSES OF ELECTROSTATIC SOLITARY WAVES IN SPACE PLASMAS

空间等离子体中静电孤波形成过程的研究

基本信息

批准号：
10440136
负责人：
OMURA Yoshiharu
金额：
$ 6.78万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

Analyzing the data by the Geotail spacecraft, we found that electrostatic solitary waves (ESW) are carried by high energy electron fluxes along the ambient magnetic field, which agree with the ESW formation model postulated from the simulations. Through statistical analysis of ESW waveforms on many orbits of the Geotail spacecraft in the magnetotail, we found that the generation regions of ESW are located near the neutral points. We performed a 2D particle simulation of magnetic reconnection, and we found that there exist acceleration processes of electrons near the reconnection points. We performed 2D simulations of the bump-on-tail instability to find that 1D solitary potentials are formed after nonlinear evolution of the instability. In the two-stream instability of electrons in a 2D.periodic system, on the other hand, we found that large amplitude potentials traveling fast along the magnetic field can exist stably through coupling with lower hybrid waves propagating slowly in the oblique direction. We also performed 2D simulations with open boundaries, injecting electron beam from one of the boundaries. We found that the ESW formation process found in the periodic system can also take place at the top portion of the electron beam traveling stably through the unperturbed warm plasma. Through theoretical analysis of the ESW formation process based on the BGK theory, we clarified that coalescence of two ESW is an irreversible process where the kinetic energy of electron holes is converted to the thermal energy of electrons trapped in the potential.

分析晶石飞机航天器的数据，我们发现静电孤立波（ESW）沿环境磁场沿高能电子通量携带，这与模拟中假定的ESW地层模型一致。通过对磁尾尾尾航天器的许多轨道上的ESW波形的统计分析，我们发现ESW的产生区域位于中性点附近。我们对磁重新连接进行了2D粒子模拟，我们发现在重新连接点附近存在电子加速过程。我们对颠簸的不稳定进行了2D模拟，发现在不稳定性的非线性演化后形成了1D孤立电势。另一方面，在2D。周期系统中电子的不稳定性中，我们发现沿着磁场快速行驶的大幅度电势可以通过与较低的混合波沿斜方向缓慢传播。我们还进行了开放边界的2D模拟，从其中一个边界注入电子束。我们发现，在周期系统中发现的ESW地层过程也可以在电子束的顶部进行，从而通过未受干扰的温暖血浆稳定传播。通过基于BGK理论的ESW形成过程的理论分析，我们澄清说，两个ESW的合并是一个不可逆的过程，其中电子孔的动能转化为被困在潜力中的电子的热能。