Statistical Relationship Between Electron Flux and Resonant Chorus Wave Power Near the Flux Limit

Abstract Electron precipitation by chorus whistler‐mode waves generated by the same electron population is expected to play an important role in the dynamics of the outer radiation belt, potentially setting a hard upper limit on trapped energetic electron fluxes. Here, we statistically analyze the relationship between equatorial electron fluxes and the power of mid‐latitude cyclotron‐resonant chorus waves precipitating these electrons, both inferred from ELFIN low‐altitude energy and pitch‐angle resolved electron flux measurements in 2020–2022. We provide clear evidence of a flux limitation coinciding with an exponential increase of precipitation. We statistically demonstrate that the actual inferred resonant wave power gains are well correlated with theoretical linear gains, as in the classical Kennel‐Petschek model, for moderately high linear gains and high fluxes. However, we also find a finite occurrence of very high fluxes, corresponding to resonant waves of moderate average amplitude, implying a softer, more dynamical upper limit than traditionally envisioned.