Role of Plasmaspheric Density in Reproducing Observed Ultra-Relativistic Electron Enhancements: A Statistical Analysis Using VERB Simulations 

Ultra-relativistic electrons in Earth’s radiation belts are strongly influenced by interactions with plasma waves and the surrounding cold plasma. Their enhancement poses a serious space-weather hazard, they can penetrate satellite shielding and damage onboard electronics.The Van Allen Probes mission was able to observe most energetic electrons exceeding 7 MeV in the Earth’s outer radiation belt. The acceleration of these particles under cold-plasma density variations has been successfully simulated for single events, but comprehensive statistical validation has not yet been performed. This study evaluates, in a statistical framework, how cold plasma density influences density-dependent wave particle interactions and the dynamics of 7.7 MeV radiation-belt electrons. We conducted three  groups of density-driven VERB (Versatile near‐Earth environment of Radiation Belts and ring current) simulations in which cold plasma density was used to scale the wave-particle diffusion coefficients: one using static density from an empirical model, one using Van Allen Probes in-situ plasma density observations, and one using plasmaspheric densities predicted by the physics-based VERB-Convection Simplified (VERB-CS) model.The study highlights the importance of coupling radiation belt models with more realistic plasmaspheric models and the need to improve plasmaspheric representations to better understand electron acceleration.