GEM: Numerical Modeling of Ultra-Low-Frequency (ULF) Waves and the Production of Geomagntically Induced Currents

地球的磁场不是静止的，而是不断波动的。在某种意义上，磁力线可以被认为是乐器上的琴弦，比如吉他或竖琴。就像竖琴的琴弦一样，这些场线的长度和密度不同，所以每条场线都以自己的频率波动。此外，地球周围的区域也可以作为一组水壶鼓之一，也有自己的频率。这些波动产生了流经太空的电流，并且经常可以在地球表面上和地表下流动。这些电流会产生重要的影响，比如电网的中断和石油和天然气管道的腐蚀。开发了一个计算机模型来描述在空间中流动的电流及其对地电流的影响。拟议的工作将进一步改进这一模型，包括基于统计模型和卫星测量的空间粒子密度的更现实的条件。这项工作也将支持研究生学习更多关于计算机模拟和问题的知识。超低频（ULF）波在近地磁层区域的能量传输中起主要作用。提出的研究的主要目标是扩展这些波的模型，并应用这些模型来更好地理解在更现实的磁层中ULF波的结构，并将空间和地面上的观测联系起来，特别是关于地磁感应电流（gic）的激发。在之前的工作中，提出者已经建立了一个偶极几何的三维数值模型来描述超低频波在内磁层中的传播。他们还开发了一个类似的球面几何代码，覆盖所有纬度。一个主要的任务将是整合偶极子码和球面码。提议者将在电离层和等离子层的经验模型的基础上，在内部磁层的潜在密度结构。该模型的结果将与范艾伦探测器和其他太空平台的数据以及地面磁力计的观测结果进行比较。该项目将研究磁层-电离层耦合系统对外部扰动的响应，例如磁层与行星际冲击的相互作用以及亚风暴期间引起的扰动。作者还将通过将模型从电离层扩展到地面来研究地面地磁感应电流（gic）的激发。该奖项反映了美国国家科学基金会的法定使命，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。

The magnetic field of the Earth is not static and is constantly fluctuating. Magnetic field lines can, in some sense, be thought of like strings on a musical instrument, like a guitar or harp. Just like the strings of a harp, these field lines are of different lengths and have different densities, so each field line fluctuates at its own frequency. In addition, the region around the Earth can also act as one of a set of kettle drums that also have their own frequency. These fluctuations give rise to electrical currents that flow through space and can often flow on and beneath the surface of the Earth. These currents can have important effects, such as disruptions in the power grid and corrosion of oil and gas pipelines. A computer model was developed to describe the currents flowing in space and their effect on ground currents. The proposed work will further improve this model by including more realistic conditions based on statistical models and satellite measurements of the density of particles in space. This work will also support a graduate student who will learn more about computer simulation as well as the issues.Ultra-low-frequency (ULF) waves play a major role in the transport of energy in the near-Earth regions of the magnetosphere. The primary goal of the proposed research is to extend our models of these waves and to apply these models to better understand the structure of ULF waves in a more realistic magnetosphere and to relate observations in space and on the ground, particularly regarding the excitation of geomagnetically induced currents (GICs). In previous work, the proposers have developed a three-dimensional numerical model in dipole geometry to describe the propagation of ULF waves in the inner magnetosphere. They have also developed a similar code in spherical geometry that covers all latitudes. A major task will be to integrate the dipole code and the spherical code. The proposers will base the underlying density structure in the inner magnetosphere on empirical models of the ionosphere and plasmasphere. The model results will be compared with data from the Van Allen Probes and other platforms in space, as well as with observations from ground magnetometers. This project will investigate the response of the magnetosphere-ionosphere coupling system to external perturbations, such as the interaction of the magnetosphere with interplanetary shocks with the perturbations induced during substorms. The proposers will also investigate the excitation of geomagnetically induced currents (GICs) on the ground by extending the model from the ionosphere through to the ground.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.