Mesoscale Magnetohydrodynamic Processes in the Magnetosphere

9314239基夫森磁层的大尺度、时间平均特性及其与太阳风和电离层的相互作用现在从稳态理论的角度得到了很好的理解。仍然存在的主要挑战是理解系统在微尺度(1RE)和我们将称为中尺度(1RE)的动力学。需要重点关注那些将太阳风的能量和动量通过磁层的磁化等离子体转移到电离层的过程。近年来，越来越明显的是，磁层的动力学本质上是片状或突发性的。间歇性似乎是这种互动的一个基本特征。虽然它们是间歇性的，但重要的过程似乎发生在与粒子回转周期相比较长的时间尺度上；相应的空间尺度与粒子回转半径相比较大，但与磁层尺寸相比较小。因此，本提案侧重于可被描述为“中尺度”或中等规模的过程。研究人员将使用航天器数据集和新的数据分析方法来描述一些中尺度结构，包括：太阳风通过磁重联过程与磁层的耦合，密度和场大小的条纹通常被解释为饱和镜像模波的特征；当连续的重新连接的等离子体到达电离层时，似乎脉动的极尖；经常以可能由爆发重联产生的方式高度结构的大规模场向电流(区域1电流)；磁尾等离子体流；间歇性或爆发式的磁尾等离子体流；以及细绳状结构的磁性特征，这些结构沿其轴线载送场向电流，并包含被扭曲磁场限制的等离子体。研究人员将开发与观测密切相关的新模型和理论。分析将从使用磁流体力学的工具开始，但完全理解可能需要等离子体动力学理论的某些方面。其目的是为解释现有的观察结果制定一个框架，并确定额外测量的需要。拟议的工作涉及似乎对相互作用的太阳风/电离层/磁层系统的动力学至关重要的过程，新的结果将阐明元素耦合过程。尽管所讨论的问题是地球磁层的问题，但其结果可能具有更广泛的意义，因为它们将适用于磁化等离子体的相互作用，无论它们在哪里：在其他磁温层、在日冕或在实验室。***

9314239 Kivelson The large scale, time-averaged properties of the magnetosphere and its interaction with the solar wind and the ionosphere are now well understood in terms of steady-state theory. The principal challenge that remains is to understand the dynamics of the system on microscales (1RE) and what we shall refer to as mesoscales ( 1RE). Attention need to be focused on those processes that transfer the energy and momentum of the solar wind through the magnetized plasma of the magnetosphere to the ionosphere. In recent years, it has become increasingly apparent that the dynamics of the magnetosphere are patchy or bursty in nature. Intermittency appears to be a fundamental feature of the interactions. Although they are intermittent, the important processes appear to occur on time scales that are long compared with particle gyroperiods; the corresponding spatial scales are large compared with particle gyroradii but small compared with magnetospheric dimensions. Hence, this proposal focuses on processes that can be characterized as "mesoscale" or intermediate in scale. The investigators will use spacecraft data sets and new data analysis approaches to characterize some of the mesoscale structures including: coupling of the solar wind to the magnetosphere through the process of magnetic reconnection, striations in density and field magnitude generally interpreted as the signature of saturated mirror mode waves; the polar cusp which appears to pulsate as successive bursts of reconnected plasma arrive at the ionosphere; large scale field- aligned currents (Region 1 currents) that are frequently highly structured in ways that may arise from bursty reconnection; the magnetotail plasma flows that are intermittent or bursty; and magnetic signatures of thin rope-like structures that carry field- aligned currents along their axes and contain plasma confined by twisted magnetic fields. The investigators will develop new models and theory with a close tie to observations. The analysis will begin by using the tools of MHD, but it is probable that full understanding will require some aspects of plasma kinetic theory. The intent is to develop a framework for the interpretation of existing observations and also to define needs for additional measurements. The proposed work addresses processes that appear to be central to the dynamics of the interacting solar wind/ionosphere/magnetosphere system, and the new results will illuminate the elemental coupling processes. Although the problems addressed are those of the terrestrial magnetosphere, the results are likely to have wider significance as they will apply to the interactions of magnetized plasmas wherever they may be: in other magnetoshperes, in the solar corona, or in the laboratory. ***