Microinjections observed by MMS FEEPS in the dusk to midnight region

Energetic electron injections are commonly observed in the premidnight to dawn regions in association with substorms. However, successive electron injections are generally separated in time by hours and are rarer in the dusk region of the inner magnetosphere. Early MMS energetic electron data taken in the dusk to premidnight regions above ~9 RE show many clusters of electron injections. These injections of 50–400 keV electrons have energy dispersion signatures indicating that they gradient and curvature drifted from earlier local times. We focus on burst rate data starting near 21:00 UT on 6 August 2015. A cluster of ~40 electron injections occurred in the following 4 h interval. The highest‐resolution data showed that the electrons in the injections were trapped and had bidirectional field‐aligned angular distributions. These injection clusters are a new phenomenon in this region of the magnetosphere. Key Points MMS FEEPS observes repetitive microinjections of 50‐400 keV electrons in the dusk to midnight region The injected electrons have bidirectional field‐aligned angular distributions The microinjections show clear energy‐time dispersions consistent with having gradient curvature drifted from the source region