Numerical study on physics on physics of auroral pattern formation and plasma elementary processes

(1)我们对极光投射在电离层上的特征模式的理论研究阐明了磁层/电离层系统中自然现象的基本等离子体物理学。首先，磁层中的电荷分离过程被认为是极光旅行浪涌、欧米茄带和涟漪的原因。(The这些极光现象的成因早已超出理论研究者的理解范围。我们的方法是独一无二的：通过粒子模拟，我们再现了电离层极光的时间/空间发展，这与观测结果是一致的。我们进一步应用基于模拟的分析问题的准稳态场向电流。类似于极光动力学的情况，我们成功地再现了观测识别的区域1和区域2场向电流的二维模拟模式。这一结果自然引出了一个新的概念，即在封闭的磁层中，由太阳风外部施加在极盖区的等离子体畸变可以产生成对的区域1/区域2场向电流。(2)利用Tsyganenko的d磁场模型，数值计算了行星际磁场影响相对较小的磁封闭区的磁漂移矢量分布。从这个图中，我们发现，在低纬边界层（LLBL）的场向电流很可能是由等离子体的压力梯度注入磁鞘。（论文将于1995年3月在SGEPSS上发表。我们还将认为，LLBL电流系统的一些功能，这已经揭示了最近的卫星观测，不能理解的模型的磁层和太阳风之间的粘性相互作用，长期以来一直被认为是一个最有可能的机制LLBL电流的产生。

(1) Our theoretical study on the characteristic pattern of auroras projected on the ionosphere has elucidated fundamental plasma physics for natural phenomena in the magnetosphere/ionosphere system. First, the processes of charge separation in the magnetosphere have been identified as being responsible for the auroral traveling surge, the omega bands, and the ripples. (The causes of these auroral phenomena had long been beyond understanding of theoretical researchers.) Our approach is unique : by using particle simulations we reproduce the temporal/spatial development of auroras on the ionosphere which is in good agreement with the observations. We further apply the simulation-based analysis to the problem of quasi-steady field-aligned currents. Similarly to the case of auroral dynamics, we successfully reproduced the observatioanlly identified pattern of region 1 and region 2 field-aligned current by the two dimensional simulations. This result leads naturally to a new concept that the paired region 1/region2 field-aligned currents can be produced from the plasma distortion in the closed magnetosphere by the solar wind externally applied in the polar cap region.(2) Using the d magnetic field model by Tsyganenko, we numerically obtained the distributions of magnetic drift vectors in the magnetically closed region where the effect of the interplanetary magnetic field is relatively small. From this plot we found that the field-aligned currents in the low-latitude boundary layr (LLBL) is likely to be caused by the pressure gradient of a plasma injected from the magnetosheath. (Paper will be presented at SGEPSS,in March 1995.) We will also argue that some features of the LLBL current system, which have been revealed by recent satellite observations, could not be understood in a model of the viscous interaction between the magnetosphere and the solar wind which had long been believed to be a most likely mechanism for the LLBL current generation.