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

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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.