GEM: MHD Mesoscale Transport at the Magnetopause

GEM：磁层顶的 MHD 中尺度输运

• 批准号: 9502907
• 负责人: Yan Song
• 金额: $ 24.18万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-06-01 至 1999-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9502907&HistoricalAwards=false
• 关键词: GEM; MHD; Mesoscale; Transport; Magnetopause

The transport of mass, momentum and energy at the magnetopause often occurs in a patchy and time-dependent manner, where MHD mesoscale physics is important. The proposed research is to study the MHD mesoscale physical processes using a recently developed macroparticle concept. In particular, the theory of driven reconnection as a process which occurs due to the dynamic interaction of the solar wind and the magnetosheath with the mangetosphere will be developed. This model will be used to quantitatively determine the threshold for the onset of reconnection, the statistical distribution of mesoscale events, and the solar wind-magnetosphere coupling parameters. When the inhomogeneities of the plasma density, velocity and magnetic field are taken into account, the interaction of magnetofluids can be described as the interaction of a number of localized filaments having a relative velocity and carrying different magnetic fields. The interactions between these filaments and between the filaments and the ambient magnetic field play a key role in the transport processes. A macro-particle description involving compressional and shear Alfvenons in cold plasma limit has been introduced to describe these localized filaments (Song and Lysak, 1994a). The properties of these Alfvenons, such as their magnetic dipole moment and polarization, have been described and it has been shown that their interaction can lead to an onset of reconnection depending on the IMF as well as on the dynamic pressure impinging on the magnetopause. The objective of this proposed research is to extend the concept of Alfvenons, which provides a theoretical basis for patchy and time- dependent driven reconnection, and to pursue further the quantitative evaluation of the solar wind-magnetosphere coupling parameter and the statistical prediction of the transient magnetic field events.

磁层顶的质量、动量和能量的输运往往以不规则的、随时间变化的方式发生，因此MHD中尺度物理在磁层顶的研究中具有重要意义。 建议的研究是研究MHD中尺度物理过程中使用最近开发的宏粒子的概念。 特别是，驱动重联的理论，这是由于太阳风和磁鞘与磁层的动态相互作用而发生的过程。 该模式将用于定量确定重联开始的阈值、中尺度事件的统计分布以及太阳风-磁层耦合参数。 当考虑等离子体密度、速度和磁场的不均匀性时，磁流体的相互作用可以描述为具有相对速度并携带不同磁场的多个局部丝的相互作用。 这些细丝之间以及细丝与环境磁场之间的相互作用在输运过程中起着关键作用。 在冷等离子体极限下，一个包含压缩和剪切Alfvenons的宏观粒子描述已经被引入来描述这些局域化的细丝（Song和Lysak，1994 a）。 这些Alfvenons的属性，如他们的磁偶极矩和极化，已被描述，它已被证明，它们的相互作用可以导致的发病重联取决于IMF以及对磁层顶上的动态压力冲击。 本研究的目的是扩展Alfvenons的概念，为斑片和时间相关的驱动重联提供理论基础，并进一步追求太阳风-磁层耦合参数的定量评估和瞬态磁场事件的统计预测。