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

超低频（ULF）波是地球磁层中的常见特征。 它们被认为在辐射带的形成和磁暴期间导致地面磁场强烈抑制的磁层环电流的形成中发挥重要作用。 波也可能在磁层亚暴、磁层振荡事件和稳定的磁层对流等现象中发挥作用。 理解超低频波强度和类型的变化的关键是理解磁平静时期磁层的基线条件。 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，工作将密切结合正在进行的研究与学生的教育。 最近的太阳黑子极小期是一个异常平静的时期，其特征是磁层处于平静、稳定状态的时间间隔延长。 虽然之前已经对磁干扰时期的ULF波进行了大量研究，但令人惊讶的是，对安静时期ULF波的分布知之甚少。 本项目将调查在最近的太阳黑子极小期磁层异常平静时太阳风在产生超低频波方面所起的作用。 它将绘制各种频带中的压缩波和环向波功率的统计图，这些功率是磁层中的位置和太阳风以及行星际磁场参数的函数。 将利用地面磁力计以及欧洲星团卫星使命和美国航天局THEMIS使命的数据绘制统计图。

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.