Cusp Turbulence and Transport and their Impact on Ionospheric Coupling

受冲击的太阳风等离子体或磁鞘为地球磁层提供了基本的输入和外边界条件。 磁鞘等离子体进入磁层和电离层的最直接的途径发生在外极尖区域。 因此，加强对磁鞘/尖点界面等离子体过程的理解对于推进磁层顶和边界层物理学是必不可少的。 由于磁层外边界附近磁场的尾部弯曲，整个磁层边界层通过这个尖点区域映射到当地中午附近的正面高纬度电离层。 虽然等离子体和磁场的相互作用在外部尖点的磁鞘和边界层的电离层连接中发挥了关键作用，很少有卫星测量在这一地区。 该项目的目标是推进等离子体，场和等离子体波相互作用的外和中高度极尖的等离子体和动量输运，场波动，以及由此产生的尖电流系统的重点知识。 研究人员将确定和测试与增强卫星提供的独特观测最相关的等离子体和场相互作用，并将其用作外尖点和中高度尖点区域粒子和场特征的基线样本。 虽然非常有限，在外部尖点的现有观测提供了足够的信息的整体几何形状和等离子体条件，应用最先进的2-D MHD和混合动力模拟的磁鞘尖点相互作用区域，包括耦合到电离层。 这样的模拟将提供信息的本地时间依赖性的流和磁场的外尖点，以及更多的非本地尖点/电离层电流系统。 了解异常的跨场动量输运对于建立尖点和向阳面电流系统的定量模型至关重要。 因此，PI将集中在剪切流驱动的不稳定性和相关的湍流和运输。 将完成对磁鞘/外尖瓣和中高度尖瓣壁边界的剪切流的真实的2-D和3-D混合模拟。 理论预测的电和磁波动谱将进行比较，特别是与观测到的ULF-ELF波谱。 反过来，交叉场传输将计算所观察到的波动光谱的基础上，以评估在尖点区域的异常扩散过程的重要性。

The shocked solar wind plasma, or magnetosheath, provides the basic input and outer boundary condition for the Earth's magnetosphere. The most direct access of this magnetosheath plasma into the magnetosphere and ionosphere occurs in the region of the outer polar cusp. Thus, an enhanced understanding of plasma processes at the magnetosheath/cusp interface is essential to the advancing magnetopause and boundary layer physics. Because of tailward bending of the magnetic field near the outer magnetospheric boundary, the entire magnetospheric boundary layer is mapped through this cusp region into the frontside, high- latitude ionosphere near local noon. Although the interaction of plasmas and fields in the outer cusp play a key role in linking the magnetosheath and boundary layer to the ionosphere, very few satellite measurements are available in this region. This project's objective is to advance the knowledge of plasma, field and plasma wave interactions in the outer and mid- altitude polar cusp with a focus on plasma and momentum transport, field fluctuations, and the resulting cusp current system. The investigators will identify and test those plasma and field interactions most relevant to enhancing unique observations available from satellite and used as a baseline sample of particle and field characteristics in the outer cusp and mid-altitude cusp regions. Although very limited, available observations in the outer cusp provide enough information on overall geometry and plasma conditions to apply state-of-the-art 2-D MHD and hybrid simulations of the magnetosheath-cusp interaction region including coupling to the ionosphere. Such simulations will provide information on the local time-dependent flows and magnetic fields in the outer cusp as well as the more nonlocal cusp/ionosphere current system. Understanding anomalous cross-field momentum transport is crucial for developing quantitative models of the cusp and dayside current systems. The PIs will therefore focus on shear-flow driven instabilities and associated turbulence and transport. Realistic 2-D and 3-D hybrid simulations of shear-flow across the magnetosheath/outer cusp and mid-altitude cusp wall boundaries will be completed. Theoretical predictions of electric and magnetic fluctuation spectra will be compared, especially with observed ULF-ELF wave spectra. In turn, cross-field transport will be calculated based on the observed fluctuation spectra to assess the importance of anomalous diffusion processes in the cusp region.