Investigation of Magnetic Reconnection in Space Plasma

本文通过对距离地球10 ~ 30 Re的地磁尾GEOTAIL数据的分析，详细研究了磁重联过程。与美国WIND和POLAR卫星以及俄罗斯Interball-Tail卫星的合作研究对阐明亚暴中的重联过程非常有用。已经提出了一些重要的结果，这些结果已经（并将）发表在科学期刊上。下面列出了一些选定的结果。GEOTAIL观测揭示了地磁尾中存在于薄片-等离子体片边界之间的慢速激波的动力学结构。通过对离子分布函数的详细分析，发现通过慢模激波的冷离子的加热有3- 20%发生在前激波区。与逆流离子束产生的电磁离子回旋波的相互作用被认为是这种加热的候选。GEOTAIL观测发现，在等离子体内部深处，存在着叶状起源的离子束沿着磁场线流动，这是磁重联形成等离子体的证据。在靠近扩散区的区域也发现了非旋向离子束的存在。这些观测结果与磁重联的计算机模拟结果吻合得很好。基于GEOTAIL与WIND和POLAR卫星的合作研究，发现磁重联在亚暴开始之前在距离-25 Re的等离子体层中开始，这表明重联至少在某些情况下会触发亚暴。GEOTAIL和Interball-Tail数据的联合研究表明，磁重联发生在13至28 Re下尾距离的等离子体层中。对快速等离子体流的统计分析表明，磁重联发生在午夜至黄昏时分，距离为20 ~ 30 Re，与亚暴的发生有关，并且随着磁重联向下尾移动，磁重联区域在黎明至黄昏方向上变宽。少

Magnetic reconnection processes have been studied in detail on the hasis of analysis of the GEOTAIL data obtained in the geomagnetic tail at distances of 10 to 30 Re away from the Earth. Collaborative studies with US satellites of WIND and POLAR and with Russian satellite Interball-Tail were highly useful to elucidate the reconnection processes in substorms. A number of important results have been brought forth, which have been (and will be) published in scientific journals. Some selected results are listed below.1.The GEOTAIL observations have revealed the kinetic structure of slow-mode shocks exising between the lobe-plasma sheet boundary in the geomagnetic tail. Based on detiled analysis of the ion distribution functions, it is found taht 3-20 % of the heating of cold ions passing through the slow-mode shock occurs in the foreshock region. Interaction with the electromagnetic ion cyclotron waves generated by the counterstreaming ion beams was suggested as a candidate of this heating … More .2.The GEOTAIL observations have found the existence of ion beams of the lobe origin streaming along the magnetic field lines deep inside plasmoids, as evidence of the plasmoid formation by magnetic reconnections. The existence of non-gyrotropic ion beams is also found in a region which is considered as near the diffusion region. These observational results agree well with those of computer simulations of magnetic reconnections.3.Based collaborative studies of GEOTAIL with WIND and POLAR satellites, it is found that the magnetic reconnection was initiated in the plasma sheet at distances of -25 Re downtail prior to a substorm onset, suggesting that the reconnections trigger substorms at least in some cases.4.Joint studies between GEOTAIL and Interball-Tail data have evidence that magnetic reconnections took place in the plasma sheet at distances between 13 and 28 Re downtail.5.Statistical analysis of fast plasma flows has revealed that magnetic reconnections occur around midnight to the duskside in the magnetotail at distances of 20 to 30 Re in association with substorm onset, and the reconnection region is widened in the dawndusk direction as it moves downtail. Less