GEM: Modeling Ultra-Low-Frequency (ULF) Waves in the Near-Earth Magnetosphere

空间物理学中的一个突出问题是能量如何在整个近空间环境中传输。超低频（0.3-3千赫）无线电波既是能量在整个磁层和电离层的传输机制，也是空间等离子体特性的重要诊断手段。该项目创建了一个新的基于物理学的模型，以更好地了解近地空间环境的动态。该项目的更广泛影响包括开发与我们对空间气象的理解和预测相关的新模型-这是《国家空间气象行动计划》中规定的一个国家优先事项-以及培训一名研究生。这项研究将涉及磁流体动力学（MHD）波代码的发展及其应用到几个问题，涉及超低频波在磁层。主要的重点将是在磁震学的问题，使用这些波作为诊断的等离子体分布在整个磁层的应用程序。这可以通过研究场线共振的性质以及通过脉冲源的超低频波的传播时间来实现。虽然以前版本的波代码要么是二维的，要么是三维的，但具有方位角对称性，代码现在允许电离层和等离子体的本地时间依赖性。这使得可以研究电离层的昼夜差异以及电导率增强的作用，例如在极光区，或耗尽，如在亚极光等离子体槽中可能发生的。包括等离子体层的不对称性将允许等离子体层结构中的黎明和黄昏差异，包括可能存在的等离子体层羽流。该研究的主要目标是开发和应用全球ULF波模型，以调查这些相互作用。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

An outstanding question in space physics is how energy is transported throughout the near space environment. Radio waves at ultra-low frequencies (0.3-3 kHz) serve as both a transport mechanism for energy throughout the magnetosphere and ionosphere and an important diagnostic of the space plasma properties. This project creates a new physics-based model to better understand the dynamics of the near-Earth space environment. The broader impacts of this project include developing new models relevant to our understanding and prediction of space weather - a national priority set out in the National Space Weather Action Plan - and the training of a graduate student.Ultra-low-frequency (ULF) waves play a major role in the transport of energy in the near-Earth regions of the magnetosphere. The research will involve the development of a magnetohydrodynamic (MHD) wave code and its application to several problems involving ULF waves in the magnetosphere. The primary focus will be on the application of this model to problems in magnetoseismology, using these waves as a diagnostic of the plasma distribution throughout the magnetosphere. This can be accomplished both by a study of the properties of field line resonances as well as through the travel times of ULF waves from an impulsive source. While previous versions of the wave code have either been two-dimensional, or three-dimensional but with azimuthal symmetry, the code now allows for local time dependence of the ionosphere and plasmasphere. This allows for studies of the day-night differences in the ionosphere as well as the role of conductivity enhancements, such as in the auroral zone, or depletions, as can occur in the sub-auroral plasma trough. Including plasmaspheric asymmetry will allow for the dawn-dusk differences in the plasmasphere structure, including the possible presence of plasmaspheric plumes. Development and application of a global ULF wave model that can investigate these interactions is the primary goal of the research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.