A Three-Dimensional Global Hybrid Simulation Study of the Bow Shock and Its Interaction with the Dayside Magnetosphere

弓形激波是太阳风与地球磁层相互作用中最重要的等离子体区域之一。卫星观测表明，在准平行激波的前震区经常出现具有空间和时间爆发的压力脉冲。这些瞬态变化进一步通过磁鞘传播，并与日侧磁层顶和磁层相互作用，导致磁层场和电流系统的不规则性。近年来的观测表明，弓形激波及其伴生波的结构是高度三维的，并且在弓形激波-磁鞘-磁层系统中发现了越来越多的新的多维现象。迄今为止，对船首激波进行的三维动力学计算很少。鉴于船首激波瞬态的三维结构在全局相互作用中的重要性，利用三维全局模型对船首激波进行研究是必要和及时的。由于离子动力学效应在弓形激波瞬态中的关键作用，将采用系统的三维全局混合模拟，并进行大规模并行计算，研究弓形激波的动力学结构及其与日侧磁层的相互作用。三维混合码是在成功的二维码的基础上发展起来的。在模拟中，弓形激波、磁鞘和磁层顶是由太阳风与地磁场自一致的相互作用形成的。主要任务是：(1)确定弯曲弓激波（包括准平行激波和准垂直激波）的三维结构和离子粒子特征；(2)通过离子动力学效应产生前激波压力脉冲和弓激波瞬态及其在磁鞘中的传输；(3)确定弓激波与观测到的尖端高能离子之间的关系。这项研究不仅有助于我们理解太阳风和磁层之间耦合的基础物理学，而且在三维动力学全球建模工作中的成功也将在磁层、天体物理学和实验室等离子体物理学的其他主题中有更广泛的应用。该模拟能够自一致地跟踪地球有效扰动的影响，将有助于区分卫星观测中的空间和时间效应。这项研究将包括奥本大学的一名研究生，它也将为美国国家科学基金会（NSF）的目标做出贡献，即为研究和教育开发和维护尖端的国家计算和信息基础设施。

The bow shock is one of the most important plasma regions in the global interaction between the solar wind and the Earth's magnetosphere. Satellite observations have shown that pressure pulses with spatial and temporal bursts are frequently present in the foreshock region of the quasi-parallel shock. These transient variations have been found to further transmit through the magnetosheath and interact with the dayside magnetopause and magnetosphere, causing irregularities in the magnetospheric field and current system. Recent observations indicate that the structure of the bow shock and its associated waves are highly three-dimensional (3-D), and more and more new multi-dimensional phenomena are being discovered in the bow shock-magnetosheath-magnetosphere system. Very few 3-D kinetic calculations of the bow shock have been conducted so far. The importance of the 3-D structure of the bow shock transients in the global interaction makes it necessary and timely to perform investigations of the bow shock using a 3-D global model. Due to the crucial roles of ion kinetic effects in the bow shock transients, a systematic 3-D global hybrid simulation, with massively parallel computations, will be performed to study the kinetic structure of the bow shock and its interaction with the dayside magnetosphere. The 3-D hybrid code has been developed on the basis of a highly successful 2-D code. In the simulation, the bow shock, magnetosheath, and magnetopause form by the self-consistent interaction between the solar wind and the geomagnetic field. The primary tasks are: (1) determination of the 3-D structure and ion particle signature of the curved bow shock, including the quasi-parallel and quasi-perpendicular shocks, (2) the generation of foreshock pressure pulses and bow shock transients by ion kinetic effects and their transmission through the magnetosheath, and (3) determination of the relationship between the bow shock and the observed cusp energetic ions.The study will not only contribute to our understanding of the fundamental physics of the coupling between the solar wind and magnetosphere, but the success in the 3-D kinetic global modeling efforts will also have broader applications in other topics of magnetospheric, astrophysical, and laboratory plasma physics. The simulation, which can track the effects of geo-effective perturbations self-consistently, will help to distinguish the spatial and temporal effects in satellite observations. The study will include a graduate student at Auburn University, and it will also contribute to the National Science Foundation (NSF)'s goal of developing and maintaining cutting edge national computing and information infrastructure for research and education.