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

GEM：太阳风和地磁活动模式对等离子体片湍流的影响

• 批准号: 0702916
• 负责人: James Weygand
• 金额: $ 17.91万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-05-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0702916&HistoricalAwards=false
• 关键词: GEM; Influence; Solar; Wind; Modes

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.

描述储存在磁尾中的电磁能如何转化为等离子体能量对我们理解磁层至关重要。 湍流被认为是一种有效的加热流体和传递动量和能量的机制，但湍流在加热地球等离子体片（PS）中的作用还没有得到很好的研究。 没有测量的空间和时间的变化特征独立，PS湍流的存在及其在能量传输中的作用仍然不确定。 该项目将检查来自PS交叉的航天器数据，以确定磁场波动并评估目前的湍流水平。 该项目将研究湍流的强度如何与地磁活动相关。 该项目将根据经验确定与湍流叶栅相关的有效磁雷诺数和能量传递率。 这项研究将利用多航天器方面的飞行器-II使命，部分分离的时间和空间特性的湍流PS波动。 为了确定磁场波动何时是湍流，将波动幅度与平均场和概率分布函数的形状进行比较。 湍流场的特征在于非高斯概率分布函数（PDF）。 将构造不同空间和时间间隔处的波动的标度指数函数和PDF，以确定何时存在间歇性湍流。 将研究湍流波动强度与地磁活动之间的相互关系。 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转移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相关联外，Cluster观测到的每次PS穿越的所有观测结果都将通过互联网提供给空间物理学界。