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On the Role of Last Closed Drift Shell Dynamics in Driving Fast Losses and Van Allen Radiation Belt Extinction
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- Author(s) / Creator(s)
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We 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 time scale
of these losses is revealed to be as short as ∼0.5–2 hr during intense magnetic storms, with some storms
demonstrating almost total loss on these time scales 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 2 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 time scale 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 ultralow
frequency 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. -
- Date created
- 2018-04-20
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- Type of Item
- Article (Published)