Satellite Remote Sensing Study of Dayside Magnetospheric Ultralow-Frequency Waves

该项目的目标是使用全球远紫外线（FUV）图像，地球的极光区域和极帽，以解决有关在Pc5频率范围（2 - 7 mHz）中出现的超低频率（ULF）波的几个问题。与传统的地面pc5探测技术（如磁力计和高频雷达）相比，全球极光图像具有更好的空间覆盖和/或分辨率，并且在磁干扰方面不受高米ULF波的电离层屏蔽效应的影响。要考虑的第一个问题是太阳风的准周期性压力变化激发Pc5波的频率。一个相关的问题是Pc5 ULF波是否优先发生在高太阳风速度下。该项目还将解决太阳风压力脉冲与磁通量转移事件在产生Pc5脉冲中的相对重要性问题。这些问题将通过分析极地UVI获得的极光图像，以及其他来自航天器（Polar, Geotail, Interball-1， Cluster和THEMIS）的原位磁场测量，使用称为s变换的光谱分析技术来解决。S-Transform使得提取全局Pc5 ULF波特征成为可能。该项目将通过确定ULF波是否直接被驱动并向反太阳方向传播，来确定磁层是否以呼吸模式或腔/波导模式响应准周期性太阳风压力变化。它将区分开尔文-亥姆霍兹驱动和压力脉冲驱动的事件，通过确定它们是否与太阳风特征有关，或者是否倾向于在高速流中发生，它将区分与磁通量转移事件相关的Pc5事件和压力脉冲驱动事件，通过检查波浪运动是否取决于磁鞘流速度和IMF方向。磁层和电离层中的超低频（ULF）波已经在各种各样的背景下进行了很长时间的研究。它们构成了对磁层响应外部干扰方式的重要诊断。这样的研究产生了大量的文献。然而，目前的理论模型的适用范围仍然不确定。这在很大程度上是由于缺乏对Pc5 ULF波的全球特征的了解。这些知识很难用传统技术获得。Pc5频率范围内的波对地球辐射带中电子的通电有重要影响。一种新的、先进的光谱分析工具（s变换）在二维极光图像中的应用可以很容易地推广到更高频率的极低频波及其跨尺度耦合的研究中

The objective of this project is to use global far-ultraviolet (FUV) images Earth's auroral regions and polar caps to address several questions concerning the occurrence of ultra-low frequency (ULF) waves in the Pc5 frequency range (2 - 7 mHz). Compared to the traditional ground-based Pc5-detecting techniques such as magnetometers and HF radars, the global auroral images have much better spatial coverage and/or resolution, and are not subject to the ionospheric screening effect of the higher-m ULF waves in terms of magnetic disturbances. The first question to be considered is how often quasi-periodic pressure variations in the solar wind excite Pc5 waves. A related question is whether or not Pc5 ULF waves occur preferentially for high solar wind speed. The project will also address the question of the relative significance of solar wind pressure pulses versus magnetic flux transfer events in generating Pc5 pulsations. These questions will be addressed by analyzing auroral images acquired by Polar UVI, along with other in situ magnetic field measurements from spacecraft (Polar, Geotail, Interball-1, Cluster, and THEMIS), using a spectral analysis technique known as the S-Transform. The S-Transform makes it possible to extract the global Pc5 ULF wave features. The project will determine if the magnetosphere responds to quasi-periodic solar wind pressure variations as a breathing mode or as a cavity/waveguide mode by determining whether or not the ULF waves are directly driven and propagate antisunward. It will distinguish between Kelvin-Helmholtz driven and pressure pulse driven events by determining whether they are associated with solar wind features or tend to occur during high speed streams, it will distinguish between Pc5 events associated with magnetic flux transfer events and pressure pulse driven events by checking if the wave motion depends on the magnetosheath flow speed and IMF orientationUltralow-Frequency (ULF) waves in the magnetosphere and ionosphere have been studied in a wide variety of contexts for a very long time. They constitute an important diagnosis of the ways the magnetosphere responds to external disturbances. A great volume of literature has resulted from such studies. Yet, the region of applicability of the current theoretical models are still uncertain. This is in large measure due to the lack of knowledge on the global characteristics of Pc5 ULF waves. This knowledge is hard to obtain using traditional techniques. Waves in the Pc5 frequency range have important effects in the energization of electrons in Earth's radiation belts. Applications of a new, advanced spectral analysis tool (the S-transform) in 2-D auroral images can be readily generalized to the study of ULF waves of higher frequencies and their cross-scale coupling