Magnetotail Physics

点击翻译按钮获取中文摘要

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.