Satellite Remote Sensing Study of Dayside Magnetospheric Ultralow-Frequency Waves

白天磁层超低频波卫星遥感研究

• 批准号: 0964396
• 负责人: Kan Liou
• 金额: $ 37.55万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0964396&HistoricalAwards=false
• 关键词: Satellite; Remote; Sensing; Study; Dayside

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

该项目的目标是利用地球极光区域和极冠的全球远紫外线 (FUV) 图像来解决有关 Pc5 频率范围 (2 - 7 mHz) 超低频 (ULF) 波发生的几个问题。 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范围和/或分辨率，并且在磁扰方面不受高m ULF波的电离层屏蔽效应的影响。 首先要考虑的问题是太阳风中的准周期性压力变化多久激发一次 Pc5 波。一个相关的问题是 Pc5 ULF 波是否会在高太阳风速时优先出现。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 脉动方面的相对重要性问题。 这些问题将通过分析 Polar UVI 获取的极光图像以及航天器（Polar、Geotail、Interball-1、Cluster 和 THEMIS）的其他原位磁场测量结果，并使用称为 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。该项目将通过确定超低频波是否直接驱动并反太阳传播来确定磁层是否以呼吸模式或空腔/波导模式响应准周期性太阳风压变化。 它将通过确定开尔文-亥姆霍兹驱动事件和压力脉冲驱动事件是否与太阳风特征相关或倾向于在高速流期间发生来区分它们，它将通过检查波运动是否取决于磁鞘流速和 IMF 方向来区分与磁通量传递事件相关的 Pc5 事件和压力脉冲驱动事件已经研究了磁层和电离层中的超低频 (ULF) 波 很长一段时间都在各种不同的环境中。它们构成了磁层对外部扰动响应方式的重要诊断。此类研究产生了大量文献。然而，当前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波的整体特征的了解。使用传统技术很难获得这些知识。 Pc5 频率范围内的波对地球辐射带中电子的激发具有重要影响。 新型、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 ULF 波及其跨尺度耦合的研究