Energetic Consequences of Fast Magnetic Reconnection

快速磁重联的能量后果

• 批准号: 0903708
• 负责人: Dana Longcope
• 金额: $ 30.2万
• 依托单位: Montana State 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: 2009-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0903708&HistoricalAwards=false
• 关键词: Energetic; Consequences; Fast; Magnetic; Reconnection

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This research aims to model the basic process by which magnetic reconnection releases energy in a magnetically dominated plasma. Since it was first proposed to explain sudden rapid energy conversion in solar flares, most investigations of magnetic reconnection in the abstract have focused on the local electric fields it requires. The results have been self-consistent local models of plasma flows and electric fields arising through small-scale phenomena such as collisions between, or dynamical separation of, electrons and ions. A small-scale electric field of this kind can produce topological changes to magnetic field lines from which the term "reconnection" derives, but cannot directly affect the magnetic energy since that is distributed throughout the large-scale magnetized volume. The research herein proposed will address the challenge, largely unaddressed to date, of how topological changes on small scales release magnetic energy stored on large scales.The proposed research will, through two complementary lines of theoretical investigation, model the dynamical response of the entire system to the sudden, localized topological change after assuming the change to have occurred. It is through this large-scale response that the magnetic field will actually achieve its lower energy state. Energy conservation demands that the dynamics somehow convert magnetic energy into other forms such as heat or bulk motion. The proposed research will develop novel time-dependent models, both analytic and numerical, from which it will be possible to answer the following questions._ What fraction of the energy released by reconnection becomes kinetic energy versus heat?_ Are Alfven waves initiated by the reconnection, and if so how much energy do they contain?_ How do large-scale dynamics react back on the small scales?Magnetic reconnection occurs in a wide variety of magnetized plasmas including the Earth's magnetosphere (as a substorm), the solar corona (as a flare), laboratory reactor experiments (as a sawtooth crash) and astrophysical accretion disks (as a jet). Due to their disparate parameters, different small-scale processes are probably responsible for the localized electric field in these different plasmas. Nevertheless, their large-scale response to small-scale topological change will probably all be very similar, since they are all described by the same physics at these scales.All work will be conducted by Physics graduate students as part of their doctoral thesis research.This proposal was submitted to the NSF-DoE Partnership in Plasma Science and Engineering joint solicitation 08-589. This award is being funded jointly by the Divisions of Physics and Astronomical Sciences of the Mathematical and Physical Sciences Directorate.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。这项研究旨在模拟磁重联在磁控制的等离子体中释放能量的基本过程。自从首次提出解释太阳耀斑中突然的快速能量转换以来，大多数关于磁重联的抽象研究都集中在它所需的局部电场上。结果是等离子体流和电场的自洽局部模型，这些模型是由电子和离子之间的碰撞或动态分离等小规模现象引起的。这种小规模的电场可以使磁力线产生拓扑变化，而“重联”一词就是由此产生的，但不能直接影响磁能，因为磁能分布在整个大规模磁化体积中。本文提出的研究将解决迄今为止尚未解决的挑战，即小尺度的拓扑变化如何释放存储在大尺度上的磁能。本研究将通过两条互补的理论研究线，在假设变化已经发生后，建立整个系统对突然的局部拓扑变化的动态响应模型。正是通过这种大规模的响应，磁场才会达到较低的能量状态。能量守恒要求动力学以某种方式将磁能转化为其他形式，如热能或体运动。拟议的研究将开发新的时间相关模型，包括解析和数值模型，从中可以回答以下问题。重联释放的能量中有多少变成了动能和热能？阿尔芬波是由重连引起的吗？如果是的话，它们包含多少能量？_大尺度动力学在小尺度上是如何反应的？磁重联发生在各种各样的磁化等离子体中，包括地球的磁层（作为亚风暴），太阳日冕（作为耀斑），实验室反应堆实验（作为锯齿状碰撞）和天体物理吸积盘（作为射流）。由于它们的参数不同，不同的小尺度过程可能是这些不同等离子体中局域电场的原因。然而，它们对小尺度拓扑变化的大尺度响应可能都非常相似，因为它们在这些尺度上都是由相同的物理描述的。所有工作将由物理学研究生进行，作为其博士论文研究的一部分。该提案已提交给NSF-DoE等离子体科学与工程合作项目联合招标08-589。该奖项由数学和物理科学理事会的物理和天文科学部联合资助。