GEM: Small and Medium Scale Modeling of the Auroral Downward Current Region

GEM：极光下行流区域的中小型模型

• 批准号: 0503314
• 负责人: Robert Ergun
• 金额: $ 30万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0503314&HistoricalAwards=false
• 关键词: GEM; Small; Medium; Scale; Modeling

The downward current region of the aurora is now recognized as an important region in the magnetospheric-ionospheric (MI) coupling process. In this region, energetic fluxes of electrons are accelerated upwards by electric fields parallel to the magnetic field. Despite the fact that the electric fields are directed downward, this region also has strong ion outflow. In fact, the ion outflow exceeds that of the upward current region. The main focus of this project is to make to understand the current-voltage relation and ion outflow in the downward current region. Three main questions will be addressed: (1) What is the relation between parallel electric fields and currents in the downward current region? (2) How do ionospheric or magnetospheric conditions affect the relation? (3) How is ion outflow modified by the combination of moving parallel electric fields and intense electrostatic turbulence? The ultimate goal of this study is to gain sufficient understanding of the downward current region to be able to incorporate its effects into global models. Direct observations of the electric fields in the downward current region indicate of that, at least in some cases, the parallel electric fields are localized and moving upwards. Observations also show that the localized parallel electric field sets up strongly unstable electron beams which, in turn, create a spatially-separated region of strong electrostatic wave turbulence with electron phase-space holes and ion cyclotron waves. The accelerated electron fluxes are substantially modified by the accompanying intense wave turbulence and electron phase-space holes. The wave turbulence also strongly heats the ions. The project is a collaborative effort carried out at the University of Colorado at Boulder by experimental space plasma physicists at the Laboratory for Atmospheric and Space Physics and theoreticians at the Center for Integrated Plasma Studies. A combination of methodologies will be used, including numerical simulations, test particle simulations and analytical modeling. Key to this study is the implementation of boundary conditions that are based on observations and use of large simulation domains to study the aggregate system of parallel electric fields and wave turbulence and evolution of electron and ion distributions. The small-scale physics will be investigated with existing 1-D and 2-D magnetized, open-boundary Vlasov codes. The medium scale physics will be investigated using analytical modeling and test-particle simulations with a newly developed code that incorporates moving double layers and realistic, time varying ion heating profiles. In addition to the direct relevance of the project to magnetosphere-ionosphere coupling, the processes being studied are also applicable to laboratory plasmas and astrophysical plasmas.

现在，Aurora的向下电流区域被认为是磁层层（MI）耦合过程中的重要区域。在该区域中，电子电场与磁场平行的电场加速了电子通量。尽管电场是向下定向的，但该区域也具有强大的离子流出。实际上，离子流出超过了向上的电流区域。该项目的主要重点是要理解向下电流区域中的电流关系和离子流出。将解决三个主要问题：（1）平行电场和向下电流区域的电流之间有什么关系？ （2）电离层或磁层条件如何影响关系？ （3）如何通过移动平行电场和强烈的静电湍流的组合来修改离子流出？这项研究的最终目标是获得对下降当前区域的充分了解，以便能够将其效应纳入全球模型。对向下电流区域中电场的直接观察表明，至少在某些情况下，平行电场是局部的，并且向上移动。观察结果还表明，局部平行的电场设置了强烈不稳定的电子束，从而用电子相位空间孔和离子循环基因波创建了一个在空间分离的区域，具有强静电波湍流。加速的电子通量通过伴随的强波湍流和电子相空间孔实质性地改变了。波湍流也强烈加热离子。该项目是在科罗拉多大学在博尔德大学的合作努力，该项目是在集成等离子体研究中心的大气与太空物理和理论家实验室的实验太空等离子体物理学家。将使用方法的组合，包括数值模拟，测试粒子模拟和分析建模。这项研究的关键是实施边界条件，这些边界条件基于观测和使用大型模拟域来研究平行电场的总体系统，波浪湍流以及电子和离子分布的演变。现有的1-D和2-D磁化的开放式弗拉索夫代码将研究小型物理。中等规模的物理学将使用新开发的代码进行分析建模和测试粒子模拟研究，该代码结合了移动的双层和逼真的，变化的离子加热曲线。除了该项目与磁层 - 离子层耦合的直接相关性外，所研究的过程还适用于实验室等离子体和天体物理等离子体。