GEM: Modeling Realistic Chorus Generation Using Large-Scale Particle-in-Cell Simulations

等离子体波在地球的磁层中无处不在，是由带电粒子与电场和磁场相互作用的集体运动形成的。了解这些波的产生和传播不仅具有重要的科学意义，而且还有助于保护太空中的人类活动和资产。在这个项目中，研究小组将研究合唱——一种在磁层内常见的哨声波，它在控制地球辐射带方面起着重要作用。该项目包括培训新进入该领域的初级科学家，并帮助他们在GEM社区发展职业。与该项目相关的外展计划也将加强当地的STEM教育。虽然人们普遍认为，大合唱是由地磁活动时期形成的高能电子的不稳定分布产生的，但大合唱的关键观测特征尚未完全了解。在这里，研究小组将使用开源的粒子单元（PIC）代码来进行大规模的第一主模拟，以探索合唱的产生机制，并产生可以直接与观测结果进行比较的特征。我们的模拟将使用观测得到的真实磁场拓扑结构和等离子体参数，并期望产生与观测一致的音调上升、带隙和重复元素的合唱。通过二维和三维PIC模拟，现有的合唱产生理论将得到检验，并揭示潜在的非线性物理。这项研究将极大地促进我们对非均匀磁场（如地球的偶极子场）中波粒相互作用的理解。这项工作将是建立基于物理的合唱波模型的重要一步，这对辐射带动力学和近地地球空间环境的可靠预测至关重要。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。

Ubiquitous in the Earth's magnetosphere, plasma waves are formed by the collective motion of charged particles interacting with electric and magnetic fields. Understanding the generation and propagation of these waves is not only of scientific importance, but it also helps to protect human activities and assets in space. In this project, the team will study chorus -- a type of whistler wave commonly observed in the inner magnetosphere that plays an important role in controlling Earth's radiation belts. This project involves training junior scientists new to the field and helping develop their careers in the GEM community. The outreach plans associated with the project will also enhance local STEM education.Although it is generally accepted that chorus is generated by the unstable distribution of energetic electrons formed during geomagnetically active times, key observational features of the chorus are not fully understood. Here the team will use an open-source particle-in-cell (PIC) code to carry out large-scale first-principal simulations to explore the generation mechanisms of chorus and produce features that can be directly compared to observations. Realistic magnetic field topology and plasma parameters derived from observations will be used in our simulations, and chorus with rising tone, band gaps and repetitive elements consistent with observations is expected to be produced. With 2D and 3D PIC simulations, existing theories of chorus generation will be tested, and the underlying nonlinear physics will be revealed. The study will greatly advance our understanding of wave-particle interaction in an inhomogeneous magnetic field like Earth's dipole field. This effort will be an important step toward building a physics-based chorus wave model, which is critical for reliable prediction of radiation belt dynamics and the near-earth geospace environment.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.