Radial diffusion simulations of the 20 September 2007 radiation belt dropout

TitleRadial diffusion simulations of the 20 September 2007 radiation belt dropout
Publication TypeJournal Article
Year of Publication2014
AuthorsAlbert, J
JournalAnnales Geophysicae
Volume32
Issue8
Pagination925 - 934
Date Published11/2014
Keywordsradial diffusion
AbstractThis is a study of a dropout of radiation belt electrons, associated with an isolated solar wind density pulse on 20 September 2007, as seen by the solid-state telescopes (SST) detectors on THEMIS (Time History of Events and Macroscale Interactions during Substorms). Omnidirectional fluxes were converted to phase space density at constant invariants M = 700 MeV G−1 and K = 0.014 RE G1/2, with the assumption of local pitch angle α ≈ 80° and using the T04 magnetic field model. The last closed drift shell, which was calculated throughout the time interval, never came within the simulation outer boundary of L* = 6. It is found, using several different models for diffusion rates, that radial diffusion alone only allows the data-driven, time-dependent boundary values at Lmax = 6 and Lmin = 3.7 to propagate a few tenths of an RE during the simulation; far too slow to account for the dropout observed over the broad range of L* = 4–5.5. Pitch angle diffusion via resonant interactions with several types of waves (chorus, electromagnetic ion cyclotron waves, and plasmaspheric and plume hiss) also seems problematic, for several reasons which are discussed.
URLhttp://www.ann-geophys.net/32/925/2014/http://www.ann-geophys.net/32/925/2014/angeo-32-925-2014.pdf
DOI10.5194/angeo-32-925-2014
Short TitleAnn. Geophys.


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