Effects of Strong Diffusion and Wave Ducting on Electron Losses Estimated by the Quasi-Linear Approach

Abstract

Chorus wave-driven electron precipitation into the atmosphere through pitch angle scattering plays a fundamental role in electron dynamics in the Earth's outer radiation belt. The efficiency of this precipitation is highly dependent on the wave intensity at the latitudes of resonance with electrons near the loss cone and can be directly inferred from measurements of precipitating and trapped electron fluxes measured by low-altitude satellites. In this study, we utilized statistical empirical whistler-mode chorus wave models and quasi-linear theory to simulate the precipitating electron spectrum observed by the Electron Losses and Fields INvestigation (ELFIN) CubeSats. Comparisons between simulations and observations during disturbed periods suggest the presence of a very small population of intense ducted waves, present only 5% of the time but carrying 6% (at 23-4 MLT) to 60% (at 4-12 MLT) of the total time-averaged wave power inside narrow field-aligned density ducts up to middle latitudes, and producing 20% (at 100 keV) to 60% (at 1 MeV) of the total time-integrated electron precipitation recorded by ELFIN at 23-12 MLT in 2020–2022, near or within the strong diffusion regime. Our study suggests that when modeling electron dynamics in future studies of Earth's magnetosphere or magnetosphere-ionosphere-atmosphere coupling processes, this small fraction of ducted intense chorus waves may need to be included as a separate wave population, in addition to the main wave populations typically captured in the existing empirical chorus wave models based on observations mainly performed at moderate latitudes.