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On the cause and extent of outer radiation belt losses during the 30 September 2012 dropout event
Author(s) -
Turner D. L.,
Angelopoulos V.,
Morley S. K.,
Henderson M. G.,
Reeves G. D.,
Li W.,
Baker D. N.,
Huang C.L.,
Boyd A.,
Spence H. E.,
Claudepierre S. G.,
Blake J. B.,
Rodriguez J. V.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2013ja019446
Subject(s) - van allen radiation belt , van allen probes , plasmasphere , geostationary orbit , geomagnetic storm , physics , electron , ring current , substorm , magnetopause , earth's magnetic field , dropout (neural networks) , ion , geophysics , daytime , radiation , magnetosphere , astrophysics , atmospheric sciences , magnetic field , astronomy , computer science , satellite , quantum mechanics , machine learning
On 30 September 2012, a flux “dropout” occurred throughout Earth's outer electron radiation belt during the main phase of a strong geomagnetic storm. Using eight spacecraft from NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Van Allen Probes missions and NOAA's Geostationary Operational Environmental Satellites constellation, we examined the full extent and timescales of the dropout based on particle energy, equatorial pitch angle, radial distance, and species. We calculated phase space densities of relativistic electrons, in adiabatic invariant coordinates, which revealed that loss processes during the dropout were > 90% effective throughout the majority of the outer belt and the plasmapause played a key role in limiting the spatial extent of the dropout. THEMIS and the Van Allen Probes observed telltale signatures of loss due to magnetopause shadowing and subsequent outward radial transport, including similar loss of energetic ring current ions. However, Van Allen Probes observations suggest that another loss process played a role for multi‐MeV electrons at lower L shells ( L * < ~4).