Energetic Electron Enhancements Near the Dayside Magnetopause: Outward Radial Transport Due To Asymmetric Drift‐Orbit Bifurcation

Abstract

The magnetopause boundary layer often exhibits flux enhancements in keV electrons. Intriguingly, these enhancements frequently occur in the afternoon sector, which is typically magnetopause‐shadowed. They are usually attributed to local production by dayside reconnection, wave‐particle interactions, or radial diffusion by ultra‐low frequency waves. However, under standard magnetospheric conditions, these mechanisms fail to explain the rapid appearance of the electron fluxes and acceleration from magnetosheath energies (tens of eV) to tens of keV. Using data from the THEMIS mission, we report an energetic electron enhancement forming on hour timescales. A test‐particle simulation shows it can result from rapid, non‐diffusive radial transport driven by asymmetric drift‐orbit bifurcation. While this does not exclude alternative interpretations involving radial diffusion, the finding underscores the role of drift‐orbit bifurcation in controlling energetic electron dynamics near the magnetopause, which should be considered alongside conventional mechanisms.