MMS FEEPS Observations of Streaming Energetic Particles After Tailward Retreat of Near-Earth X-Line

Abstract:

In Phase 2 of the Magnetospheric Multiscale (MMS) mission, the orbit apogee was raised to 25 Earth radii allowing for observations deeper into the Earth’s magnetotail. On 17 July 2017, multiple elements of the modern-day Heliophysics System Observatory observed an isolated substorm sequence with MMS located about 22 Earth radii in the nightside magnetosphere, multiple geostationary observatories (GOES, LANL), and inner magnetosphere observations including the Van Allen Probes. The MMS spacecraft observed an ion jet reversal indicating the tailward retreat of the near-Earth X-line (NEXL) and several plasmoids flowing rapidly Earthward. This substorm process is described in detail in the companion paper by Baker et al. and concludes with streaming energetic electrons up to ~500keV. The substorm process is studied in this paper with an emphasis on the final streaming energetic electrons.