权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

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.

通过对Geotail卫星观测数据的分析，发现静电孤立波（ESW）是由高能电子流沿着环境磁场传播的，这与模拟中提出的ESW形成模型相一致。通过对Geotail航天器在磁尾多个轨道上ESW波形的统计分析，发现ESW的产生区域位于中性点附近。我们对磁场重联进行了二维粒子模拟，发现在重联点附近存在电子加速过程。我们进行了二维模拟尾部凸点不稳定性，发现一维孤立势形成后的非线性演化的不稳定性。另一方面，在二维周期系统中电子的双流不稳定性中，我们发现沿着磁场快速传播的大振幅势可以通过与斜向缓慢传播的低杂波耦合而稳定存在。我们还进行了2D模拟与开放的边界，注入电子束从一个边界。我们发现，ESW形成过程中发现的周期系统也可以发生在顶部的电子束稳定地通过未扰动的温暖等离子体。基于BGK理论对ESW的形成过程进行了理论分析，阐明了两个ESW的聚并是一个不可逆的过程，电子空穴的动能转化为电子在势阱中的热能。