Responses of relativistic electron fluxes in the outer radiation belt to geomagnetic storms

TitleResponses of relativistic electron fluxes in the outer radiation belt to geomagnetic storms
Publication TypeJournal Article
Year of Publication2015
AuthorsXiong, Y, Xie, L, Pu, Z, Fu, S, Chen, L, Ni, B, Li, W, Li, J, Guo, R, Parks, Gk.
JournalJournal of Geophysical Research: Space Physics
Pagination9513–9523
Date Published11/2015
Keywordsenergy dependence; Geomagnetic storm; Radiation belts; relativistic electrons; Solar wind
AbstractGeomagnetic storms can either increase or decrease relativistic electron fluxes in the outer radiation belt. A statistical survey of 84 isolated storms demonstrates that geomagnetic storms preferentially decrease relativistic electron fluxes at higher energies, while flux enhancements are more common at lower energies. In about 87% of the storms, 0.3–2.5 MeV electron fluxes show an increase, whereas 2.5–14 MeV electron fluxes increase in only 35% of the storms. Superposed epoch analyses suggest that such “energy-dependent” responses of electrons preferably occur during conditions of high solar wind density which is favorable to generate magnetospheric electromagnetic ion cyclotron (EMIC) waves, and these events are associated with relatively weaker chorus activities. We have examined one of the cases where observed EMIC waves can resonate effectively with >2.5 MeV electrons and scatter them into the atmosphere. The correlation study further illustrates that electron flux dropouts during storm main phases do not correlate well with the flux buildup during storm recovery phases. We suggest that a combination of efficient EMIC-induced scattering and weaker chorus-driven acceleration provides a viable candidate for the energy-dependent responses of outer radiation belt relativistic electrons to geomagnetic storms. These results are of great interest to both understanding of the radiation belt dynamics and applications in space weather.
URLhttp://onlinelibrary.wiley.com/wol1/doi/10.1002/2015JA021440/full
DOI10.1002/2015JA021440
Short TitleJ. Geophys. Res. Space Physics


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