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Magnetic reconnection in the Earth's magnetosphere

地球磁层中的磁重联

基本信息

批准号：
15340161
负责人：
NAGAI Tsugunobu
金额：
$ 10.05万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-15340161/
关键词：
magnetic reconnection substorm magnetotail Hall current electron heating magnetogydrodynamics anomalous resistivity simulation

项目摘要

To understand magnetotail dynamics, it is essential to determine where magnetic reconnection takes place in the near-Earth plasma sheet during substorms. The Geotail spacecraft thoroughly surveyed the near-Earth magnetotail at radial distances of 10-31 Re during the years 1995-2003. Thirty-four clear reconnection events were identified using the criterion of strong electron acceleration. Various solar wind parameters prior to each reconnection events were examined in order to fine the factor controlling the location of the magnetic reconnection site in the magnetotail. The same analyses were carried out for fast tailward flow events. The most important factor was determined to be the solar wind energy input, which can be expressed by -Vx x Bs, where Vx is the x component of the solar wind velocity and Bs is the southward component of the interplanetary magnetic field. It is likely that higher energy input, rather than the total amount of energy input, primarily controls the location of magnetic reconnection; magnetic reconnection takes place closer to the Earth when the input energy is higher. A large number of simulations for magnetic reconnection in different codes were carried out. It is demonstrated that magnetic reconnection is quickly triggered only under the current sheet thickness smaller than ion inertial length. A multiple X lines commonly form spontaneously, and several X lines coexist and develop. In the developing phase of magnetic reconnection, electron two-stream instability provides electron acceleration and mixing. The nonlinear phase of the electron two-stream instability produces electrostatic solitary waves (ESWs), which are frequently observed by the spacecraft Geotail.

为了了解磁尾动力学，必须确定亚暴期间近地等离子体片中发生磁重联的位置。1995-2003年期间，Geotail航天器在10-31 Re的径向距离上对近地磁尾进行了彻底调查。34个明确的重联事件被确定使用强电子加速的标准。为了确定控制磁尾磁重联点位置的因素，对每次重联事件前的各种太阳风参数进行了检验。对快速尾流事件也进行了同样的分析。最重要的因素被确定为太阳风能量输入，它可以表示为-Vx x Bs，其中Vx是太阳风速度的x分量，Bs是行星际磁场的向南分量。很可能是较高的能量输入，而不是能量输入的总量，主要控制磁场重联的位置;当输入能量较高时，磁场重联发生在更靠近地球的地方。利用不同的程序对磁场重联进行了大量的模拟。结果表明，只有当电流片厚度小于离子惯性长度时，才能快速触发磁重联。多个X线通常自发形成，并且几个X线共存并发展。在磁场重联的发展阶段，电子双流不稳定性提供了电子加速和混合。电子双流不稳定性的非线性相位产生静电孤立波（ESW），这是经常被探测器Geotail观测到的。