Collaborative Research: GEM--Determining the Global Impact of Nonlinear Wave-Particle Interactions in the Radiation Belts

The Earth’s radiation belts are a dynamic and complex plasma environment. Large amplitude waves can nonlinearly accelerate particles to energies high enough to pose a radiation hazard in the near-Earth space environment. These large amplitude waves are common but only occur in small regions for a short period of time. Therefore, it is unknown if such a drastic but localized acceleration can have an impact on a global scale. By modeling the nonlinear wave-particle interaction in a global scale radiation belt model, this research will conclusively show the importance of these large-scale waves on the whole space environment. The research will promote the development of two early-career researchers. Additionally, undergraduate students at a minority-serving institution will be trained as an integral part of this project. The physics of wave-particle interactions in the Earth’s radiation belts is well understood in the linear and quasilinear regimes, but large amplitude waves create a complex nonlinear problem. Significant theoretical and computational work has been done to understand how nonlinear wave-particle interactions can efficiently energize or pitch angle scatter high-energy electrons. As successful as local studies of nonlinear wave-particle interactions have been in explaining the micro-scale physics of a particle in a large amplitude wave, it has yet to be demonstrated that these nonlinear effects lead to global, macro-scale changes in the radiation belts. In this study, we will use theory, modeling, and data analysis to answer the fundamental science question: Do nonlinear wave-particle interactions affect the radiation belts on a global scale? This will be done by calculating advection and diffusion coefficients from nonlinear wave-particle interactions that can be directly included in the K2 radiation belt model. K2 is a global scale radiation belt model based on the stochastic differential equation (SDE) framework and accurately captures wave-particle interactions at an individual particle level. By simulating real events with K2, the sensitivity of the whole radiation belt system to localized large amplitude waves can be quantified. 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.