A Proposal for the Measurement and Analysis of Extremely Low Frequency (ELF) Waves at South Pole Station

南极站极低频（ELF）波测量和分析的建议

• 批准号: 0513990
• 负责人: Marc Lessard
• 金额: $ 13.51万
• 依托单位: University of New Hampshire
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-10-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0513990&HistoricalAwards=false
• 关键词: Proposal; Measurement; Analysis; Extremely; Low

This project will detect and record magnetic field fluctuations in the Extremely Low Frequency (ELF) range at South Pole Station. The range of frequencies being measured (1 to 350 Hz) encompasses interesting and important phenomena related to magnetosphere-ionosphere coupling. The primary objective is to characterize auroral ion cyclotron waves, which, according to theory, modulate precipitating electron fluxes, causing the flickering in auroral luminosity emissions. Substantial evidence now exists in support of this theory, although the excitation mechanism responsible for the ion cyclotron waves is somewhat uncertain. Perhaps the most well-developed theory suggests that the waves result from an electron beam instability. In any case, the frequency of the flickering or, equivalently, the frequency of the ground-based observations of ion cyclotron waves can be used to infer the altitude of the excitation mechanism, since the wave frequency depends on the strength of the known background magnetic field. As such, the information that will be acquired as part of this project can be used to test models of auroral acceleration mechanisms. The second objective of this project is to study dispersive ELF waves, a type of wave that has been reported in the literature only a few times, but one that may provide important information regarding substorm onset or, perhaps, boundaries of open and closed magnetic fields. A first step in the project is to identify the wave mode and to determine the location and geomagnetic conditions under which these waves are observed. Ultimately the most important parameter to be quantified is energy transfer, which occurs via Poynting fluxes and particle energy. A significant fraction of the particle energy flux is associated with auroral phenomena, so to a great extent our knowledge of magnetosphere-ionosphere coupling depends on how well we understand auroral processes.

该项目将探测和记录南极站极低频（ELF）范围的磁场波动。所测量的频率范围（1至350赫兹）包括与磁层-电离层耦合有关的有趣和重要的现象。主要目的是表征极光离子回旋波，根据理论，它调制沉淀的电子通量，导致极光光度发射中的闪烁。现在有大量证据支持这一理论，尽管引起离子回旋波的激发机制有些不确定。也许最完善的理论认为，引力波是电子束不稳定的结果。在任何情况下，闪烁的频率，或者等价地，离子回旋波的地面观测频率，都可以用来推断激发机制的高度，因为波的频率取决于已知背景磁场的强度。因此，作为该项目的一部分，将获得的信息可用于测试极光加速机制的模型。该项目的第二个目标是研究色散极低频波，这是一种在文献中只报道过几次的波，但它可能提供有关亚暴发生或开放和封闭磁场边界的重要信息。该项目的第一步是确定波的模式，并确定观测到这些波的位置和地磁条件。最终要量化的最重要参数是能量传递，它通过坡印亭通量和粒子能量发生。粒子能量通量的很大一部分与极光现象有关，因此在很大程度上，我们对磁层-电离层耦合的认识取决于我们对极光过程的理解程度。