On the role of last closed drift shell dynamics in driving fast losses and Van Allen radiation belt extinction

TitleOn the role of last closed drift shell dynamics in driving fast losses and Van Allen radiation belt extinction
Publication TypeJournal Article
Year of Publication2018
AuthorsOlifer, L, Mann, IR, Morley, SK, Ozeke, LG, Choi, D
JournalJournal of Geophysical Research: Space Physics
Date Published04/2018
Keywordsinner magnetosphere; magnetopause shadowing; Radiation belts; Van Allen Probes
AbstractWe present observations of very fast radiation belt loss as resolved using high‐time resolution electron flux data from the constellation of Global Positioning System (GPS) satellites. The timescale of these losses is revealed to be as short as ∼0.5 − 2 hours during intense magnetic storms, with some storms demonstrating almost total loss on these timescales and which we characterize as radiation belt extinction. The intense March 2013 and March 2015 storms both show such fast extinction, with a rapid recovery, while the September 2014 storm shows fast extinction but no recovery for around two weeks. By contrast, the moderate September 2012 storm which generated a three radiation belt morphology shows more gradual loss. We compute the last closed drift shell (LCDS) for each of these four storms and show a very strong correspondence between the LCDS and the loss patterns of trapped electrons in each storm. Most significantly, the location of the LCDS closely mirrors the high time resolution losses observed in GPS flux. The fast losses occur on a timescale shorter than the Van Allen Probes orbital period, are explained by proximity to the LCDS, and progress inward, consistent with outward transport to the LCDS by fast ULF wave radial diffusion. Expressing the location of the LCDS in L*, and not model magnetopause standoff distance in units of RE, clearly reveals magnetopause shadowing as the cause of the fast loss observed by the GPS satellites.
URLhttps://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025190
DOI10.1029/2018JA025190
Short TitleJ. Geophys. Res. Space Physics


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