Energetic Electron Microinjections Observed by MMS in the Dusk Plasma Sheet and Drift Resonance Interpretation

Microinjection phenomena, characterized by dispersive oscillations of electron fluxes at the Pc5 period and bi-directional pitch angle anisotropy, are frequently observed by Magnetospheric Multiscale in the dusk to midnight plasma sheet. In this paper, two such events are analyzed and the features of toroidal mode drift resonance measured meanwhile are shown in detail. The prominent observation is that the fluctuations of the electron flux and the electric field have either -90 degrees or +90 degrees phase difference at the resonant energy, and the phase difference rises as the energy increases. We extend the present theory for drift resonance of toroidal mode wave with only the equatorial moving electrons in a dipole field to include bouncing electrons. The predicted phase differences based on the new theory are consistent well with the observations in the microinjection events. It is thus suggested that drift resonance may act as the forming mechanism for the observed microinjections.

Automated summary

This paper analyzes the features of drift resonance in microinjection phenomena and proposes a new theory that includes bouncing electrons. The observed phase differences in microinjection events are consistent with the predicted phase differences based on the new theory, suggesting that drift resonance may act as the forming mechanism for microinjections.