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

空间物理学中一个悬而未决的问题是能量是如何在临近空间环境中传输的。超低频(0.3-3千赫)的无线电波既是整个磁层和电离层的能量传输机制，也是空间等离子体性质的重要诊断手段。该项目创建了一个新的基于物理的模型，以更好地了解近地空间环境的动力学。该项目的更广泛影响包括开发与我们对空间天气的了解和预测有关的新模式--这是国家空间气象行动计划规定的一项国家优先事项--以及培训一名研究生。这项研究将涉及开发磁流体动力(MHD)波程序，并将其应用于涉及磁层中的超低频波的几个问题。主要的焦点将是该模型在磁震学问题上的应用，使用这些波作为整个磁层中等离子体分布的诊断。这既可以通过研究场线共振的性质来实现，也可以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WAVE代码要么是二维的，要么是三维的，但具有方位对称性，现在该代码允许电离层和等离子体层的当地时间依赖。这使得能够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，或在亚极光等离子体槽中可能发生的损耗。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的差异，包括可能存在的等离子体层羽流。这项研究的主要目标是开发和应用一个可以研究这些相互作用的全球URF波模型。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.