Association of Relativistic Electron Microbursts Duration With Chorus Wave Properties

Abstract

Relativistic electron microbursts are correlated with resonant scattering by whistler-mode chorus waves. Here, we use chorus wave properties obtained from Van Allen Probe A to calculate the duration of relativistic microbursts. A detailed quantitative comparison between observed and calculated microburst durations shows consistent ranges and similar correlations with $L$ shell and magnetic local time (MLT). The most apparent trend is in MLT: microburst duration increases from midnight through the dawn sector but decreases after noon. These results highlight the primary role of chorus waves in driving microbursts. Furthermore, we build a constraint on the upper magnetic latitude boundary $\left({\lambda }_2\right)$ of chorus waves that can induce 1 MeV microbursts. The constraint is dependent on MLT. On the dayside, the optimal ${\lambda }_2$ typically exceeds $36°$, which is higher than on the nightside, suggesting ducted chorus propagation dominates. Chorus waves with higher ${\lambda }_2$ are generally more effective in triggering relativistic microbursts.