Modeling Unsteady Reconnection in the Magnetotail

磁尾不稳定重联建模

• 批准号: 0903890
• 负责人: Mikhail Sitnov
• 金额: $ 29.24万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2012-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0903890&HistoricalAwards=false
• 关键词: Modeling; Unsteady; Reconnection; Magnetotail

The onset of reconnection in tail-like plasma configurations is one of the most fundamental energy transformation processes in space plasmas. It results in acceleration and heating of plasma particles, new plasma structures and turbulence. It gives rise to substorms in Earth's magnetosphere. Similar processes occur in the magnetospheres of Jupiter, Saturn, Mercury, other planets and their moons, in the solar corona and in the laboratory plasmas, including the laboratory experiments on magnetic reconnection. This project will examine kinetic models of magnetic reconnection in Earth's magnetotail. In the magnetotail the onset of reconnection is determined not only by different motions of ions and electrons but also by different motions of the electrons trapped inside the current sheet and those passing through the tearing instability region. It also depends on the structure of the current sheet, whether the reconnecting current layer is embedded into a thicker plasma sheet or not. Significant progress in understanding of the magnetotail reconnection becomes possible because of the availability of( a) nonlocal kinetic stability analysis codes, (b) new models of thin current sheets embedded into thicker plasma sheets or split into two current layers, and (c) kinetic particle simulation codes with open boundaries (as opposed to periodic boundary conditions) for both fields and particles. The goal of this project is to use and develop the above tools and models to investigate: 1) the kinetic mechanisms of the reconnection onset in the magnetotail, 2) different types of thin current sheets that precede the onset and arise in process of reconnection, and 3) the regimes of reconnection characteristic of the tail-like, collisionless plasmas. New regimes of reconnection available in collisionless tail-like systems, are very different from the standard picture of magnetic reconnection, with the electron dissipation region at the magnetic X-point and with the fast reconnection mediated by whistler or kinetic Alfven waves and dominated by the Hall fields. The project will develop new tools (thin current sheet models and full-particle simulations with open boundaries) that will be useful in other areas of plasma physics and astrophysics, magnetic-confinement fusion, solar physics, and plasma propulsion. The work will also provide hands-on research training for student summer interns via The Johns Hopkins University Applied Physics Laboratory summer intern program.

尾状等离子体中的重联是空间等离子体中最基本的能量转换过程之一。它导致等离子体粒子的加速和加热，新的等离子体结构和湍流。它在地球的磁层中产生亚暴。类似的过程发生在木星、土星、水星、其他行星及其卫星的磁层、日冕和实验室等离子体中，包括关于磁场重联的实验室实验。该项目将研究地球磁尾磁场重联的动力学模型。 在磁尾中，重联的开始不仅取决于离子和电子的不同运动，而且还取决于被捕获在电流片中的电子和穿过撕裂不稳定区的电子的不同运动。它还取决于电流片的结构，重连电流层是否嵌入到较厚的等离子体片中。在理解磁尾重联方面取得重大进展是可能的，因为（a）非局部动力学稳定性分析代码，（B）新模型的薄电流片嵌入到较厚的等离子体片或分裂成两个电流层，和（c）动力学粒子模拟代码与开放的边界（相对于周期性边界条件）的字段和粒子。本项目的目标是使用和发展上述工具和模型来研究：1）磁尾重联开始的动力学机制，2）在重联开始之前和重联过程中出现的不同类型的薄电流片，以及3）尾状无碰撞等离子体的重联特征。在无碰撞的尾状系统中，新的重联机制与磁重联的标准图像非常不同，电子耗散区位于磁X点，快速重联由哨声波或动力学阿尔芬波介导，并由霍尔场主导。该项目将开发新的工具（薄电流片模型和开放边界的全粒子模拟），这些工具将在等离子体物理学和天体物理学、磁约束聚变、太阳物理学和等离子体推进等其他领域中发挥作用。这项工作还将通过约翰霍普金斯大学应用物理实验室暑期实习生计划为学生暑期实习生提供实践研究培训。