Global Distributions of Ultra-Low Frequency (ULF) Wave Power in the Quiet Magnetosphere

超低频(ULF)波是地球磁层的一个常见特征。它们被认为在形成辐射带和形成磁层环电流方面发挥了重要作用，而磁层环电流在磁暴期间对地面磁场产生了强烈的抑制。这些波也可能在磁层亚暴、锯齿事件和稳定的磁层对流等现象中发挥作用。了解超低频波强度和类型的变异性的关键是了解磁层在磁平静时期的基线状况。除了加强我们对磁层基线状态的了解外，该项目还将产生重大的教育效益。这项研究将包括一些本科生，这项工作将把正在进行的研究与学生的教育紧密结合起来。最近的太阳黑子极小期是一个异常平静的时期，标志着磁层处于平静、稳定状态的时间间隔延长。虽然之前已经对磁扰动期的超低频波做了很多研究，但令人惊讶的是，人们对安静时期的超低频波的分布知之甚少。这个项目将研究在最近的太阳黑子极小期期间太阳风在超低频波的产生中所起的作用，当时磁层异常平静。它将绘制不同频段的纵波和环波功率随磁层位置以及太阳风和行星际磁场参数变化的统计图。统计地图将使用地面磁力计以及来自欧洲集群卫星飞行任务和美国航天局THEMIS飞行任务的数据编制。

Ultra-Low Frequency (ULF) waves are a common feature in Earth's magnetosphere. They are thought to play important roles in the formation of the radiation belts and the formation of the magnetospheric ring current that causes strong suppression of the magnetic field on the ground during magnetic storms. The waves may also play a role in such phenomena as magnetospheric substorms, sawtooth events, and steady magnetospheric convection. A key to understanding the variability of the intensities and types of ULF waves is understanding the baseline condition of the magnetosphere during magnetically quiet times. In addition to enhancing our understanding of the baseline state of the magnetosphere this project will also have significant educational benefits. The research will include a number of undergraduate students and the work will closely integrate the research being done with the education of the students. The most recent sunspot minimum was an unusually quiet period that was marked by extended intervals during which the magnetosphere was in a quiet, steady state. While much prior research has been done on ULF waves during magnetically disturbed times, surprisingly little is known about the distribution of ULF waves during quiet times. This project will investigate the role the solar wind plays in the generation of ULF waves during the recent sunspot minimum when the magnetosphere was unusually quiet. It will develop statistical maps of the compressional and toroidal wave power in various frequency bands as a function of location in the magnetosphere and the solar wind and interplanetary magnetic field parameters. The statistical maps will be developed using ground-based magnetometers as well as data from the European Cluster satellite mission and the NASA THEMIS mission.