Fast diffusion of ultra-relativistic electrons: March 17, 2015 storm event
Tuesday, September 29, 2015
Allison N Jaynes1, Daniel N. Baker2, Shri Kanekal3, Xinlin Li1, David Malaspina4, Scot Richard Elkington5 and Ashar Ali2, (1)University of Colorado at Boulder, LASP, Boulder, CO, United States, (2)University of Colorado at Boulder, Boulder, CO, United States, (3)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (4)University of Colorado, Boulder, Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, (5)Laboratory for Atmospheric and Space Physics, Boulder, CO, United States
Abstract:
In recent times, the radial diffusion mechanism has fallen out of favor as the dominant process of of outer belt electron acceleration. In its place, energy diffusion enacted by higher frequency waves (local acceleration) has been shown to be the more significant process. However, radial diffusion driven by low-frequency waves likely plays the leading role in radiation belt acceleration events during the absence of intense VLF chorus. In this study, we present observations of the fast diffusion of ultra-relativistic outer belt electrons following the March 17, 2015 storm period. Several days after the storm main phase, during which a significant dropout occurred, very high energy electrons (3-8 MeV) re-appeared in the heart of the outer belt and were subsequently driven inward, presumably by strong ULF waves as observed with Van Allen Probes fields instruments. We examine this fast diffusion rate along with the local and global distribution of relevant plasma waves to make the claim that the energization of ultra-relativistic electrons is driven primarily by low-frequency waves following the March 17, 2015 storm. Additionally, we compare this diffusion rate to previous periods of high geomagnetic activity to find that this ultra-fast radial diffusion of ultra-relativistic electrons is unique so far in the Van Allen Probes era.
