Combined Particle and Fluid Simulations of the Magnetosphere, Its Boundary Layers and Current Systems

9321665 Winglee MHD是用来模拟磁层动力学的主要工具之一。 我们的分析和数值计算表明，电阻欧姆定律MHD的基础上是不合适的磁层，因为大部分的等离子体和能量传输发生在薄的边界层，并作为一个结果给出了一个不完整的描述磁层电流系统。 我们能够确定的第一次的内在粒子的影响，控制（一）磁层边界层的结构，（二）在电流片需要重新连接的耗散和（三）映射到和出的昼侧和夜侧极光区的电流。 这些影响是确定从粒子/两种流体模拟，提供了一个进步单流体MHD通过消除由施加异常电阻率引起的歧义，并通过解决该地区的映射1 ND 2极光电流。 拟议的工作旨在发展（i）二维和三维区域粒子模拟，以确定磁层顶、LLBL和磁尾内粒子分布的结构、电流系统和特性，（ii）在3-D提供从这些区域发出进入极光区的电流的完整全球地图，以及它们通过他们产生的磁层顶和磁尾电流片的耗散，和（iii）交叉校准粒子和流体模拟与Tsyganenko模型测试建模的准确性，更重要的是，以帮助在一个模型的建设，预测磁层和极光电流的平均响应。 三维全球模拟将基于一套修改后的双流体方程，该方程已针对粒子模拟进行了测试校准。 它使用了广义欧姆定律的修正版，并加入了一个描述电子的附加方程 导致昼侧和夜侧极光流的运动。 粒子模拟将采用一种新的有限差分算法来求解场解，这种算法可以使网格间距可变，从而能够对动力学过程进行大规模区域建模。 拟议的工作将对磁层物理学有重要的应用，提供进出磁层的磁力线和电流的全球测绘，并确定与临界边界层有关的结构和粒子分布。 它有可能在磁场扰动地面观测和极光椭圆运动与航天器现场磁场扰动观测以及极光椭圆运动与航天器现场高能粒子观测之间建立直接联系。 此外，通过与Tsyganenko模型的比较，我们将能够构建一个平均磁层模型，该模型可用于预测由Kp确定的盛行太阳风条件下的磁层活动。 所有这些应用都符合NSF磁层计划的重要目标。 ***

9321665 Winglee MHD is one of the main tools used to model the dynamics of the magnetosphere. We show both analytically and numerically that the resistive Ohm's law on which MHD is based is not appropriate for the magnetosphere because much of the plasma and energy transport occurs across thin boundary layers and as a result gives an incomplete description of the magnetospheric current system. We are able to identify for the first time the intrinsic particle effects that control (i) the structure of magnetospheric boundary layers, (ii) the dissipation in current sheets needed for reconnection and (iii) the currents that map into and out of the dayside and nightside auroral regions. These effects are determined from particle/two fluid simulations that provide an advancement over single fluid MHD by removing ambiguities arising from the imposition of anomalous resistivity and by resolving the mapping of the region 1 nd 2 auroral currents. The proposed work seeks development of (i) regional particle simulations in both 2-D and 3-D to identify the structure, current system, and properties of the particle distributions within the magnetopause, LLBL and magnetotail, (ii) modified two-fluid simulations in 3-D to provide full global mapping of the currents emanating from these regions into the auroral region and their effect on the global dynamics through the dissipation they produce on the magnetopause and magnetotail current sheets, and (iii) cross-calibration between the particle and fluid simulations with the Tsyganenko model to test the accuracy of the modeling and, more importantly, to aid in the construction of a model that predicts the average response of the magnetosphere and the auroral currents. The 3-D global simulations are to be based on a modified set of two-fluid equations that have been test calibrated against particle simulations. It uses a modified version of the generalized Ohm's law and incorporates an additional equation describing the electron motion responsible for the dayside and nightside auroral currents. The particle simulations will incorporate a new finite-difference algorithm for the field solutions that can enable variable grid spacing and thereby enable large scale regional modelling of kinetic processes. The proposed work will have important applications to magnetospheric physics by providing global mapping of both magnetic field lines and currents into and out of the magnetosphere, and by identifying the structure and particle distributions associated with critical boundary layers. It has the potential of providing a direct link between ground-based observations of magnetic field perturbations and the motion of the auroral oval with in-situ spacecraft observations of magnetic field perturbations and the motion of the auroral oval with in-situ spacecraft observations of energetic particles. In addition, through the comparison with the Tsyganenko model we will be able to construct an average magnetospheric model that can be used to predict the magnetospheric activity as determined by Kp for prevailing solar wind conditions. All these applications meet important objectives of NSF's Magnetospheric Program. ***