Bursty Bulk Flow Turbulence as a Source of Energetic Particles to the
Outer Radiation Belt
Abstract
We report observations of a Bursty Bulk Flow (BBF) penetrating to the
outer edge of the radiation belt. The turbulent BBF braking region is
characterized by ion velocity fluctuations, magnetic field (B)
variations, and intense electric fields (E). In this event, energetic
(>100 keV) electron and ion fluxes are appreciably
enhanced. Importantly, fluctuations in energetic electrons and ions
suggest that they are locally energized. Using correlation distances and
other observed characteristics of turbulent E, test-particle simulations
support that local energization by E favors higher-energy electrons and
leads to an enhanced energetic shoulder and tail in the electron
distributions. The energetic shoulder and tail can be amplified to MeV
energies by adiabatic transport into the radiation belt where
|B| is higher. This analysis suggests that turbulence
generated by BBFs can, in part, supply energetic particles to the outer
radiation belt and that turbulence can be a significant contributor to
particle acceleration.