On the cause and extent of outer radiation belt losses during the 30 September 2012 dropout event

Authors

D. L. Turner, University of California - Los AngelesFollow
V. Angelopoulos, University of California - Los AngelesFollow
S. K. Morley, Los Alamos National LaboratoryFollow
M. G. Henderson, Los Alamos National LaboratoryFollow
Geoffrey Reeves, Los Alamos National LaboratoryFollow
W. Li, University of California - Los Angeles
D. N. Baker, University of Colorado BoulderFollow
Chia-Lin L. Huang, University of New Hampshire - Main CampusFollow
A. J. Boyd, University of New Hampshire - Main CampusFollow
Harlan E. Spence, University of New HampshireFollow
S. Claudepierre, Aerospace CorporationFollow
J. B. Blake, Aerospace CorporationFollow
J. V. Rodriguez, University of Colorado Boulder

Abstract

Abstract

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). Key Points Dropout events can encompass the entire outer radiation belt Dropouts can result in >90% losses and be a hard reset on the system Loss at L > ∼4 is dominated by MP shadowing and outward transport.

Department

Physics

Publication Date

3-2014

Journal Title

Journal of Geophysical Research: Space Physics

Publisher

American Geophysical Union Publications

Digital Object Identifier (DOI)

10.1002/2013JA019446

Document Type

Article

Recommended Citation

Turner, D. L., et al. (2014), On the cause and extent of outer radiation belt losses during the 30 September 2012 dropout event, J. Geophys. Res. Space Physics, 119, 1530–1540, doi:10.1002/2013JA019446

Rights

©2014. American Geophysical Union. All Rights Reserved.