Radiation belt electron flux dropouts during the main phase of geomagnetic storms have received increasing attention in recent years. Here we focus on a rarely reported nonstorm time dropout event observed by Van Allen Probes on 24 September 2013. Within several hours, the radiation belt electron fluxes exhibited a significant (up to 2 orders of magnitude) depletion over a wide range of radial distances (L > 4.5), energies (∼500 keV to several MeV) and equatorial pitch angles (0°≤αe≤180°). STEERB simulations show that the relativistic electron loss in the region L = 4.5–6.0 was primarily caused by the pitch angle scattering of observed plasmaspheric hiss and electromagnetic ion cyclotron waves. Our results emphasize the complexity of radiation belt dynamics and the importance of wave-driven precipitation loss even during nonstorm times.
Bibliographical noteFunding Information:
We acknowledge the ?Quantitative Assessment of Radiation Belt Modeling? focus group for motivating this study, acknowledge J. H. King, N. Papatashvilli, and CDAWeb for the use of interplanetary parameters and magnetospheric indices, and acknowledge the University of Iowa as the source for the EMFISIS data (this acknowledgment does not imply endorsement of the publication by the University of Iowa or its researchers), acknowledge V. Angelopoulos, J. W. Bonnell, F. S. Mozer, A. Roux, R. E. Ergun, U. Auster, K. H. Glassmeier, and W. Baumjohann for the use of THEMIS data. This work was supported by the National Natural Science Foundation of China grants 41422405, 41274169, 41274174, 41174125, 41131065, 41421063, 41231066, and 41304134, the Chinese Academy of Sciences grant KZCX2-EW-QN510 and KZZD-EW-01-4, the National Key Basic Research Special Foundation of China grant 2011CB811403, and the Fundamental Research Funds for the Central UniversitiesWK2080000077. Data are available at the following websites: http://cdaweb.gsfc.nasa.gov/cdaweb/istp_public/ (geomagnetic activity indices, interplanetary parameters and THEMIS), http://emfisis.physics.uiowa.edu/Flight/ (EMFISIS), http://www.rbsp-ect.lanl.gov/data_pub/ (ECT), http://www.space.umn.edu/rbspefw-data/ (EFW) and http://satdat.ngdc.noaa.gov/sem/poes/data/ (POES).
©2016. American Geophysical Union. All Rights Reserved.
Copyright 2016 Elsevier B.V., All rights reserved.
- numerical modeling
- plasmaspheric hiss
- precipitation loss
- radiation belt dropout
- wave-particle interaction