Nonlinear Theory of Anomalous Resistivity for Buneman Instability

Buneman 不稳定性的反常电阻率非线性理论

• 批准号: 0837878
• 负责人: Peter Yoon
• 金额: $ 21.06万
• 依托单位: University of Maryland, College Park
• 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: 2009-07-15 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0837878&HistoricalAwards=false
• 关键词: Nonlinear; Theory; Anomalous; Resistivity; Buneman

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project combines a theoretical and numerical study of one of the mechanisms that may initiate magnetic reconnection in a geomagnetic substorm. The general mechanism is an enhancement in the electrical resistivity of the plasma brought on by a plasma instability. The effective electrical resistivity is referred to as "anomalous resistivity." Magnetic reconnection is one of the most important research topics in contemporary space plasma physics. Although it is at the core of many astrophysical, space, and magnetospheric processes, there are still many issues associated with this fundamental process that have yet to be understood. The onset process and the mechanism which breaks the frozen-in-flux condition are among them. It is widely recognized that the anomalous resistivity that arises from small-scale kinetic plasma instabilities is one of the crucial factors that can lead to the onset of reconnection by breaking the magnetohydrodynamics (MHD) frozen-in-flux condition. Of the many possible plasma instabilities relevant for collisionless reconnection, this project will focus on the Farley-Buneman (FB) instability (also known as the two-stream instability). Theoretical computation of anomalous resistivity in the literature has been limited to quasilinear formalism. However, recent numerical simulations show that numerically tabulated anomalous resistivity from FB instability can be orders of magnitude higher than the theoretical prediction. This shows that nonlinear theory is called for. This project develops a self-consistent nonlinear theory of anomalous resistivity for the FB instability. The customary text book theory is inapplicable for the FB instability since it is a reactive instability. The project will perform a quantitative analysis based upon the nonlinear theory, and compare the theoretical results with results from numerical simulations. In view of the importance of anomalous resistivity phenomena for a variety of problems in magnetospheric and solar-terrestrial physics, astrophysics, and even laboratory plasma physics, the research will have far-reaching consequences. From the perspective of fundamental plasma physics, the research will lead to a new way of analyzing nonlinear stages of plasma instabilities. The plasma kinetic theory developed by the early pioneers of modern plasma physics is valid only for weakly unstable kinetic instabilities. In plasmas, kinetic instabilities form only a small subset of problems. More general reactive instabilities are important for many situations, and are far more prevalent. For this important class of instabilities, there is currently no theory to analyze their fully nonlinear behavior. Even though the immediate goal of this research is to investigate only the nonlinear phase of the Farley-Buneman instability, the underlying nonlinear theory will be valid for any reactive instability.

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。该项目结合了对可能在地磁亚暴中启动磁重联的机制之一的理论和数值研究。一般的机制是由等离子体不稳定性带来的等离子体电阻率的增强。有效电阻率被称为“异常电阻率”。“磁场重联是当代空间等离子体物理中最重要的研究课题之一。虽然它是许多天体物理学、空间和磁层过程的核心，但仍然有许多与这一基本过程相关的问题尚未被理解。其中包括磁通冻结的发生过程和打破磁通冻结的机理。人们普遍认为，由小尺度动力学等离子体不稳定性引起的异常电阻率是通过打破磁流体动力学（MHD）冻结通量条件而导致重联开始的关键因素之一。在与无碰撞重联相关的许多可能的等离子体不稳定性中，本项目将重点关注Farley-Buneman（FB）不稳定性（也称为双流不稳定性）。文献中异常电阻率的理论计算一直局限于拟线性形式。然而，最近的数值模拟表明，从FB不稳定性的数值表异常电阻率可以比理论预测高几个数量级。这表明非线性理论是必要的。本计画针对FB不稳定性发展一个自洽的非线性异常电阻率理论。由于FB不稳定性是一种反应性不稳定性，因此传统的教科书理论不适用。本计画将以非线性理论为基础进行定量分析，并将理论结果与数值模拟结果进行比较。鉴于异常电阻率现象对磁层和日地物理学、天体物理学甚至实验室等离子体物理学中的各种问题的重要性，这项研究将产生深远的影响。从等离子体基本物理的角度，该研究将为分析等离子体不稳定性的非线性阶段提供一种新的途径。由现代等离子体物理学的早期先驱发展的等离子体动力学理论仅对弱不稳定的动力学不稳定性有效。在等离子体中，动力学不稳定性只是问题的一小部分。更一般的反应不稳定性对许多情况都很重要，而且更为普遍。对于这类重要的不稳定性，目前还没有理论来分析它们的完全非线性行为。尽管本研究的直接目标是只研究Farley-Buneman不稳定性的非线性相，但潜在的非线性理论对任何反应不稳定性都是有效的。