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Empirically estimated electron lifetimes in the Earth’s radiation belts: 1. Observations
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  • Seth G. Claudepierre,
  • Qianli Ma,
  • Jacob Bortnik,
  • Thomas Paul O'Brien,
  • Joseph F. Fennell,
  • J Bernard Blake
Seth G. Claudepierre
The Aerospace Corporation

Corresponding Author:[email protected]

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Qianli Ma
University of California Los Angeles
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Jacob Bortnik
University of California Los Angeles
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Thomas Paul O'Brien
The Aerospace Corporation
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Joseph F. Fennell
The Aerospace Corporation
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J Bernard Blake
The Aerospace Corporation
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Abstract

We use measurements from NASA’s Van Allen Probes to calculate the decay time constants for electrons over a wide range of energies (30 keV - 4 MeV) and values ( = 1.3 - 6.0) in the Earth’s radiation belts. Using an automated routine to identify flux decay events, we construct a large database of lifetimes for near-equatorially-mirroring electrons over a 5-year interval. We find long lifetimes (~100 days) in the inner zone that are largely independent of energy, contrasted with shorter, energy-dependent lifetimes (~1-20 days) in the slot region and outer zone. We compare our lifetime calculations with prior empirical estimates and find good quantitative agreement. The comparisons suggest that some prior estimates may overestimate electron lifetimes between ≈ 2.5-4.5 due to instrumental effects and/or background contamination. Previously reported two-stage decays are explicitly demonstrated to be a consequence of using integral fluxes.