Magnetotail Physics

在亚暴发展阶段，等离子体片从薄的伸展构型变化到亚暴扩张阶段的宽偶极子构型。磁尾电流主要从黎明到黄昏流过等离子体片。这种交尾电流的一部分被转移到电离层，在那里产生极光。拟议项目的总体目标是更好地了解磁尾电流是如何在各种条件下由单个粒子携带的。将特别强调内侧尾巴。载流离子将通过追踪单个粒子的轨道来研究。在磁尾的不同区域发现了几种类型的离子轨迹。环电流和辐射带的绝热轨道在低海拔地区存在。在最感兴趣的区域，混沌、准绝热和囚禁轨道交替在更远的地方。在遥远的尾巴上，准绝热轨道通常占主导地位。电子在将要研究的所有区域中的行为都是绝热的。分析的第一阶段将这些粒子组合在一起，生成一系列自洽的等离子体片模型，每个模型都应用于尾部的一小部分。在自洽模型中，带电粒子必须携带产生磁场的电流，在磁场中跟踪轨道。然后，将本地模型耦合起来，以研究洋流分流和更大规模的马尾结构。最后，必须绘制这些结构的地图并将其与电离层耦合。

The plasma sheet varies from a thin stretched configuration during substorm growth phase to a broad dipolar configuration during substorm expansion phase. Magnetotail electric currents flow primarily from dawn to dusk through the plasma sheet. Part of this cross-tail current is diverted to the ionosphere, where auroras are produced. The overall goal of the proposed project is to obtain a better physical understanding of how magnetotail current is carried by individual particles under a variety of conditions. Special emphasis will be placed on the inner tail. The current carrying ions will be studied by tracing individual particle orbits. Several types of ion trajectories are found in different regions of the magnetotail. Adiabatic orbits characteristic of the ring current and radiation belts are present at low altitudes. Chaotic, quasi-adiabatic, and trapped orbits alternate farther out, in the region of most interest. Quasi-adiabatic orbits usually dominate in the distant tail. Electrons behave adiabatically in all the regions that will be studied. The first stage of analysis combines these groups of particles to generate a series of self-consistent plasma sheet models, each applying to a small region of the tail. In a self-consistent model, the charged particles must carry the electric current that generates the magnetic field in which the orbits were traced. The local models then will be coupled in order to study current diversion and larger scale mangetotail structures. Finally, the structures must be mapped and coupled to the ionosphere.