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

该项目将在南极站探测和记录极低频(ELF)范围内的磁场波动。正在测量的频率范围(1至350赫兹)包括与磁层-电离层耦合有关的有趣而重要的现象。主要目标是描述极光离子回旋波的特征，根据理论，这种回旋波调制了沉淀电子通量，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，尽管离子回旋波的激发机制有些不确定。也许最成熟的理论认为，这些波是由电子束不稳定引起的。在任何情况下，离子回旋波的闪烁频率或相当于地面观测的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而获得的信息可用于测试极光加速机制模型。该项目的第二个目标是研究色散ELF波，这种波在文献中只被报道过几次，但可能提供关于亚暴开始或开放和关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的参数是能量传递，这是通过坡印亭通量和粒子能量发生的。很大一部分粒子能流与极光现象有关，因此我们对磁层-电离层耦合的了解在很大程度上取决于我们对极光过程的理解程度。

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.