磁鞘晨昏不对称性的实验室研究

Earth's magnetosphere and magnetosheath, formed by the interaction of solar wind with Earth's intrinsic magnetic field, are the channel that the plasma and the energy of the solar wind entry into and thus influence the geospace environment. They play important roles in geospace research and space whether forecasting. Satellite's observation provides a clear magnetosheath dawn-dusk asymmetry close to the magnetopause, which can further causes the dawn-dusk asymmetry of the cold ion component which comes from the solar wind in plasma sheet of the magnetosphere. The density and temperature of the cold ion component are always higher on the dawn flank. It's not clear what causes the dawn-dusk asymmetry. Parker spiral configuration of the interplanetary magnetic field (IMF) in the solar wind at the bow shock was conventionally used to explain the magnetosheath dawn-dusk asymmetry. But we found that the Hall effect alone can also result in a clear magnetosheath dawn-dusk asymmetry close to the magnetopause in our laboratory experiments on magnetized laser plasma facility and our simulation recently. In the present project, we will explore the magnetosheath dawn-dusk asymmetry close to the magnetopause caused by the Hall effect or the synergistic action of the Hall effect with the IMF by means of experiment on the magnetized laser plasma facility and simulation. It can benefit to our understanding of the magnetosphere.

太阳风与地磁场相互作用会形成地磁层和地磁层前面的磁鞘。磁鞘和地磁层是太阳风的等离子体和能量进入并影响地球近地空间环境的通道，在空间物理和空间天气预报中发挥着关键的作用。大量卫星观测数据表明磁层顶附近的磁鞘存在晨昏(dawn-dusk)不对称性，这种不对称性可能会进而导致地磁层等离子体中来自于太阳风的冷离子成分明显的晨昏不对称，地磁层晨侧冷离子成分的密度和温度总是高于昏侧。过去的研究认为磁鞘等离子体的晨昏不对称性是由于弦激波处太阳风携带的Parker螺旋线形状的行星际磁场所致，但最近我们通过磁化激光等离子体实验并结合数值模拟研究发现，Hall效应也可以导致磁层顶附近的磁鞘明显的晨昏不对称。本项目将采用磁化激光等离子体物理实验并结合数值模拟手段，系统研究Hall效应以及Hall效应与行星际磁场共同作用导致的磁层顶附近磁鞘的晨昏不对称性，这将有助于我们更好地理解地磁层的结构。

实验发现等离子体流在偶极磁场作用下形成不对称的磁鞘结构，磁场方向相反时磁鞘的不对称性反转，这显示霍尔效应可能是产生磁鞘晨昏不对称性的一种重要机制；实验上系统研究了磁场区大于等离子体流尺寸的情况下等离子体流在强磁场中的演化过程，发现了横向磁场中等离子体流产生的抗磁腔以及磁场和等离子体界面的不稳定性的演化规律，实验室内重现了地磁层中爆炸等离子体现象；实验发现背景气体中磁准直外流从高准直射流、紧凑射流到椭圆瓣的结构演化决定于外阿尔芬马赫数，为众多的磁准直天体外流形貌的形成机制提供了一种统一的物理模型；我们将发现的物理规律应用于激光聚变中、提出了“充磁黑腔”激光聚变新方案，可以大幅度降低传统充气腔的充气密度、抑制激光受激散射过程从而提高聚变增益。在传输线、磁场线圈和电容器模块方面对强磁场设备进行了持续技术改进，从而简化实验运行、产生更高强度磁场和多种磁场位型。