How relativistic electrons are lost is an important question surrounding the complex dynamics of the Earth's outer radiation belt. Radial loss to the magnetopause and local loss to the atmosphere are two main competing paradigms. Here on the basis of the analysis of a radiation belt storm event on 27 February 2014, we present new evidence for the electromagnetic ion cyclotron (EMIC) wave-driven local precipitation loss of relativistic electrons in the heart of the outer radiation belt. During the main phase of this storm, the radial profile of relativistic electron phase space density was quasi-monotonic, qualitatively inconsistent with the prediction of radial loss theory. The local loss at low L shells was required to prevent the development of phase space density peak resulting from the radial loss process at high L shells. The rapid loss of relativistic electrons in the heart of outer radiation belt was observed as a dip structure of the electron flux temporal profile closely related to intense EMIC waves. Our simulations further confirm that the observed EMIC waves within a quite limited longitudinal region were able to reduce the off-equatorially mirroring relativistic electron fluxes by up to 2 orders of magnitude within about 1.5 h.
Bibliographical noteFunding Information:
This work was supported by the National Natural Science Foundation of China grants 41422405, 41631071, 41774170, 41274169, 41274174, 41174125, 41131065, 41421063, 41231066, and 41304134, the Chinese Academy of Sciences grant KZCX2-EW-QN510 and KZZD-EW-01-4, the CAS Key Research Program of Frontier Sciences grant QYZDB-SSW-DQC015, the National Key Basic Research Special Foundation of China grant 2011CB811403, and the Fundamental Research Funds for the Central Universities WK2080000077. We acknowledge the University of Iowa as the source for the EMFISIS data (this acknowledgement does not imply endorsement of the publication by the University of Iowa or its researchers). The data are available at the websites: RBSP-EMFSIS: http://emfisis.physics.uiowa.edu/Flight/, RBSP-ECT: http://www.rbsp-ect.lanl. gov/data_pub/, and POES: https:// cdaweb.sci.gsfc.nasa.gov/index.html/.
©2017. American Geophysical Union. All Rights Reserved.
- EMIC waves
- electron loss
- pitch angle scattering
- radial diffusion
- radiation belts
- wave-particle interaction