Inward radial diffusion driven by ULF waves has long been known to be capable of accelerating radiation belt electrons to very high energies within the heart of the belts, but more recent work has shown that radial diffusion values can be highly event-specific, and mean values or empirical models may not capture the full significance of radial diffusion to acceleration events. Here we present an event of fast inward radial diffusion, occurring during a period following the geomagnetic storm of 17 March 2015. Ultrarelativistic electrons up to ∼8 MeV are accelerated in the absence of intense higher-frequency plasma waves, indicating an acceleration event in the core of the outer belt driven primarily or entirely by ULF wave-driven diffusion. We examine this fast diffusion rate along with derived radial diffusion coefficients using particle and fields instruments on the Van Allen Probes spacecraft mission.
Bibliographical noteFunding Information:
A. N. Jaynes acknowledges the use of funds from NASA’s Van Allen Probes ECT project, through JHU/APL contract 967399 under prime NASA contract NAS5-01072. All data are publicly available from NASA SPDF CDAWeb, including the Van Allen Probes and OMNI solar wind data.
- ULF waves
- radial diffusion
- radiation belts