GEM: Structure of Cold Plasma Density Fluctuations in the Terrestrial Inner Magnetosphere

This project will improve our ability to predict space weather triggered by energetic particles surrounding the Earth. The particles can sometimes precipitate into the upper atmosphere in rapid bursts. The resulting disturbances in the upper atmospheric plasma degrade the accuracy and reliability of Global Positioning System (GPS) navigation signals, with direct consequences for aviation, military operations, and civilian transportation systems that depend on precise positioning. This project will produce comprehensive characterization of fluctuations in energetic particle densities and shed light on how they eventually create upper atmospheric disturbances. The researchers will use both in situ and remote sensing measurements from multiple spacecraft. Beyond the scientific advances, the project will strengthen the nation's space weather workforce by training the next generation of researchers and incorporating new findings into university curricula. This project will systematically quantify cold plasma density fluctuations parameters in Earth's inner magnetosphere (their amplitudes, temporal characteristics, spatial structure, and relationship to magnetic field fluctuations) using multi-point data from multiple spacecraft missions. The work addresses three core questions: what are the amplitudes and temporal properties of cold plasma density fluctuations and how do they relate to local magnetic field variations; what is the spatial structure of these fluctuations across a range of scales, from small field-aligned duct-like enhancements to large-scale features such as the plasmapause and plasma plume; and how do both the amplitudes and spatial-temporal structure of these fluctuations depend on location within the magnetosphere and the level of geomagnetic activity. Because cold plasma density is the fundamental parameter controlling wave propagation and wave-particle interactions in the inner magnetosphere, a comprehensive statistical map of its fluctuation properties is essential for understanding radiation belt dynamics and energetic electron precipitation. Energetic electron precipitation into the upper atmosphere locally disturbs ionospheric electron density, introducing errors in satellite-based navigation signals with potential consequences for civilian and defense positioning systems. The results will fill a critical observational gap and provide the empirical foundation needed to improve radiation belt models and space weather forecasting tools that protect satellite operations and ground-based technological infrastructure. 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.