Correlated Discontinuous Energetic and Auroral Electron Precipitations Poleward of the Outer Radiation Belt Boundary

Auroral and energetic electron precipitation (EEP) are key diagnostics for the coupling between the solar wind, magnetosphere, and ionosphere. We report coordinated observations of structured, discontinuous EEP near the outer radiation belt boundary (oRB) using FY-3E and DMSP measurements. These events are characterized by latitudinally separated precipitations for electrons up to hundreds of keV and spatial coincidence between EEP and localized auroral structures (double ovals, transpolar arcs, diffuse aurora superposed with discrete filaments, etc.). Two principal scattering pathways for EEPs are identified: (a) field-line curvature scattering (FLCS) in the locally stretched plasma sheet (PS); and (b) wave-particle interaction (WPI), for example, by whistler waves. Statistics over 114 events show that the discontinuous EEP and auroral precipitations can result from all types of mechanisms mentioned above. Since EEPs are confined to closed field lines, their co-existence indicates the closed field line topology. Main auroral ovals lie roughly along the oRB, while poleward auroral structures mostly occur within 10°MLAT from oRB. In a discrete arc event, the FLCS-driven EEP shows a distinct flux-energy profile from the monoenergetic auroral electrons. The observations suggest a plausible mechanism where localized structures in the equatorial plane both stretch field lines to scatter energetic PS electrons and generate parallel potential to accelerate auroral electrons. In a diffuse aurora event, the diffuse flux-energy profiles extend from auroral to FY energies (1–100 s keV), suggesting broadband scattering by waves. The coordinated observations of correlation between discontinuous energetic and auroral electron precipitations help reveal the mesoscale magnetosphere-ionosphere coupling along field lines.