Observation of an Electron Microburst With an Inverse Time-Of-Flight Energy Dispersion

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 & SIM;0.2 of the equatorial electron gyrofrequency scattered the microburst.

Automated summary

Interactions between whistler mode chorus waves and electrons have a significant impact on particle acceleration and loss in the outer radiation belt. This study focuses on electron microburst precipitation, a rapid release of intense electrons, and aims to understand the scattering mechanism between microburst and chorus waves, particularly the dominant resonance harmonic. Through observation and analysis using the time-of-flight energy dispersion, a clear example of the inverse time-of-flight dispersion is presented, supporting the Miyoshi-Saito time-of-flight model.