GEM: Influence of Solar Wind and Modes of Geomagnetic Activity on Plasma Sheet Turbulence

描述储存在磁尾中的电磁能量如何转化为等离子体能量对于我们理解磁层是至关重要的。湍流被认为是加热流体和传递动量和能量的有效机制，但湍流在加热地球等离子体片（PS）中的作用尚未得到很好的研究。如果没有独立表征时空变化的测量，PS湍流的存在及其在能量输运中的作用仍然不确定。该项目将检查来自PS穿越的航天器数据，以确定磁场的波动并评估目前存在的湍流水平。该项目将研究湍流强度与地磁活动之间的关系。该项目将经验性地确定与湍流级联相关的有效磁雷诺数和能量传递速率。本研究将利用Cluster-II任务的多航天器方面来部分分离湍流PS波动的时空特性。为了确定何时磁波动是湍流的，将波动幅度与平均场和概率分布函数的形状进行比较。湍流场用非高斯概率分布函数（pdf）来表征。将构建不同空间和时间间隔波动的标度指数函数和pdf，以确定何时存在间歇性湍流。紊流波动强度与地磁活动之间的关系将被研究。将对太阳风参数和湍流波动进行类似的研究。PS湍流的总体重要性将通过比较能量传递率与磁层总能量来评估。除了将湍流波动与太阳风和地磁活动联系起来外，群集观测到的每次PS穿越的所有观测结果将通过互联网提供给空间物理学界。

A description of how electromagnetic energy stored in the magnetotail is transferred to plasma energy is critical to our understanding of the magnetosphere. Turbulence is known to be an effective mechanism for the heating of fluids and for the transfer of momentum and energy, but the role of turbulence in heating Earth's plasma sheet (PS) has not been well studied. Without measurements to characterize spatial and temporal variations independently, the existence of PS turbulence and its role in energy transport remain uncertain. This project will examine spacecraft data from PS crossing to determine the fluctuations in the magnetic field and assess the level of turbulence that is present. The project will examine how the strength of the turbulence correlates with geomagnetic activity. The project will empirically determine the effective magnetic Reynolds number and the energy transfer rate associated with the turbulent cascade. This study will use the multi-spacecraft aspect of the Cluster-II mission to partially separate temporal and spatial properties of turbulent PS fluctuations. To determine when the magnetic fluctuations are turbulent, the fluctuation amplitude will be compared to the mean field and the shape of the probability distribution functions. Turbulent fields are characterized by non-Gaussian probability distribution functions (PDFs). Scaling exponential functions and PDFs of the fluctuations at different spatial and temporal separations will be constructed to determine when intermittent turbulence is present. The correlation between the intensity of the turbulent fluctuations and the geomagnetic activity will be investigated. A similar study will be done with the solar wind parameters and the turbulent fluctuations. The overall importance of PS turbulence will be assessed by comparing the energy transfer rate with the total magnetospheric energy. In addition to correlating the turbulent fluctuations with the solar wind and geomagnetic activity, all the observations of each PS traversal observed by Cluster will be made available to the space physics community over the internet.