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

这个项目将在地球磁层中开发和应用一类新的电流片平衡。这些平衡将是解析解，并且可以使用等离子体的粒子胞内（PIC）动力学模拟来启动它们时间演化的动力学研究。将要解决的问题包括：地球磁层中许多观测到的电流片结构能否由这类新平衡的稳定成员来模拟？非驱动（自发）重连对初始条件有多敏感？是什么潜在的不稳定因素使流动表不稳定？磁重联是如何在地球磁尾中触发的？地球磁层顶不对称重联的开始如何用新的平衡来模拟？新平衡模型在磁尾中瞬态重联的表现如何？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、低混合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产生的电流片。对非平衡条件如何向平衡条件演化的研究将提高我们对磁层动力学的理解。这项研究涉及等离子体物理学的许多不同领域。即使在磁层物理学的主要焦点内，这项研究也会产生各种各样的影响。它将为磁层顶重联的模拟提供新的不对称动态电流片平衡，并为更广泛的磁尾和磁鞘重联模拟提供对称平衡。此外，它可以帮助我们理解在磁层中观察到的许多广泛的稳定电流片，这些电流片不能被模拟为哈里斯电流片平衡。它的潜在影响扩展到发生无碰撞磁重联的所有等离子体域：磁层、太阳风、太阳日冕、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“锯齿”不稳定性被认为涉及重联。该项目还将通过培训一名研究生在等离子体理论、模拟和数据可视化方面产生教育影响。

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.