Kinetic Structure, Stability, and Dynamics of Current Sheets in Magnetospheric Plasmas

该项目将开发和使用地球磁层中一类新的电流片平衡。 这些平衡将是解析解，并可用于启动其时间演化的动力学研究，使用粒子在细胞（PIC）动力学模拟的等离子体。 其中的问题，将解决以下问题：许多观察到的电流片配置在地球的磁层可以模拟稳定的成员，这类新的平衡？非驱动（自发）重联对初始条件的敏感性如何？使电流片不稳定的潜在不稳定性是什么？地球磁尾的磁场重联是如何触发的？新的平衡能在多大程度上模拟地球磁层顶不对称重联的开始？新的平衡模型在磁尾的瞬时重联开始时能有多好？ 二维和三维的PIC模拟将确定这些不同的动力学平衡对各种等离子体过程的稳定性，包括撕裂，低杂漂移和其他不稳定性。此外，初步结果表明，非平衡初始条件可以导致自生电流片。对非平衡条件如何向平衡条件演变的研究将提高我们对磁层动力学的理解。这项研究与等离子体物理学的许多不同领域都相关。即使是在磁层物理学的主要重点范围内，研究也将产生各种影响。它将提供新的非对称动力学电流片平衡的磁层顶的重联模拟以及对称平衡的更广泛的一类重联模拟中的磁尾和磁鞘。此外，它可以有助于我们理解的许多广泛的稳定的电流片已被观察到的磁层，不能建模为哈里斯电流片平衡。它的潜在影响延伸到发生无碰撞磁重联的所有等离子体域：磁层、太阳风、日冕、实验室重联实验和环形磁聚变装置，其中抑制约束和加热的“磁”不稳定性被认为涉及重联。该项目还将通过培训等离子体理论，模拟和数据可视化的研究生产生教育影响。

This project will develop and employ a new class of current sheet equilibria in Earth's magnetosphere. These equilibria will be analytic solutions and can be used initiate dynamical studies of their time evolution using particle-in-cell (PIC) kinetic simulations of the plasma. Among the issues that will be addressed are the following: Can the many observed current sheet configurations in Earth's magnetosphere be modeled by the stable members of this new class of equilibria? How sensitive is undriven (spontaneous) reconnection to initial conditions? What are the underlying instabilities which destabilize current sheets? How is magnetic reconnection triggered in Earth's magnetotail? How well can the initiation of asymmetric reconnection at Earth's magnetopause be modeled by the new equilibria? How well can the new equilibria model transient reconnection onset in the magnetotail? The PIC simulations in two and three dimensions will determine the stability of these diverse kinetic equilibria against a variety of plasma processes including tearing, lower hybrid drift and other instabilities. In addition, preliminary results have demonstrated that non-equilibrium initial conditions can lead to self-generated current sheets. The investigation of how non-equilibrium conditions can evolve toward an equilibrium condition will improve our understanding of the dynamics of the magnetosphere.The research has relevance to many different fields of plasma physics. Even within the main focus of magnetospheric physics the research will have diverse impacts. It will provide novel asymmetric kinetic current sheet equilibria for simulations of reconnection at the magnetopause as well as symmetric equilibria for a wider class of simulations of reconnection in the magnetotail and magnetosheath. Furthermore, it can contribute to our understanding of the many broad stable current sheets which have been observed in the magnetosphere and which cannot be modeled as Harris current sheet equilibria. Its potential impact extends to all plasma domains where collisionless magnetic reconnection occurs: to the magnetosphere, to the solar wind, to the solar corona, to laboratory reconnection experiments and to toroidal magnetic fusion devices in which "sawtooth" instabilities which inhibit confinement and heating are believed to involve reconnection. The project will also have an educational impact through the training of a graduate student in plasma theory, simulations, and data visualization.