Observation of an Electron Microburst With an Inverse Time-Of-Flight Energy Dispersion
Published in Geophysical Research Letters, 2023
Abstract: Interactions between whistler mode chorus waves and electrons are a dominant mechanism for particle acceleration and loss in the outer radiation belt. One form of this loss is electron microburst precipitation: a sub-second intense burst of electrons. Despite previous investigations, details regarding the microburst-chorus scattering mechanism---such as dominant resonance harmonic---are largely unconstrained. One way to observationally probe this is via the time-of-flight energy dispersion. If a single cyclotron resonance is dominant, then higher energy electrons will resonate at higher magnetic latitudes: sometimes resulting in an inverse time-of-flight dispersion with lower-energy electrons leading. Here we present a clear example of this phenomena, observed by a FIREBIRD-II CubeSat on 27 August 2015, that shows good agreement with the Miyoshi-Saito time-of-flight model. When constrained by this observation, the Miyoshi-Saito model predicts that a relatively narrowband chorus wave with a ~0.2 of the equatorial electron gyrofrequency scattered the microburst.