Browsing by Author "Elkington, S.R."

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    Dependence of EMIC wave parameters during quiet, geomagnetic storm, and geomagnetic storm phase times
    (Wiley, 2016) Halford, A.J.; Fraser, B.J.; Morley, S.K.; Elkington, S.R.; Chan, A.A.
    As electromagnetic ion cyclotron (EMIC) waves may play an important role in radiation belt dynamics, there has been a push to better include them into global simulations. How to best include EMIC wave effects is still an open question. Recently many studies have attempted to parameterize EMIC waves and their characteristics by geomagnetic indices. However, this does not fully take into account important physics related to the phase of a geomagnetic storm. In this paper we first consider how EMIC wave occurrence varies with the phase of a geomagnetic storm and the SYM-H, AE, and Kp indices. We show that the storm phase plays an important role in the occurrence probability of EMIC waves. The occurrence rates for a given value of a geomagnetic index change based on the geomagnetic condition. In this study we also describe the typical plasma and wave parameters observed in L and magnetic local time for quiet, storm, and storm phase. These results are given in a tabular format in the supporting information so that more accurate statistics of EMIC wave parameters can be incorporated into modeling efforts.
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    Effects of magnetic drift shell splitting on electron diffusion in the radiation belts
    (Wiley, 2016) Zheng, Liheng; Chan, A.A.; O’Brien, T.P.; Tu, W.; Cunningham, G.S.; Albert, J.M.; Elkington, S.R.
    Drift shell splitting in the presence of pitch angle scattering breaks all three adiabatic invariants of radiation belt electron motion and produces new diffusion terms that fully populate the diffusion tensor in the Fokker-Planck equation. The Radbelt Electron Model (REM) solves such a Fokker-Planck equation and is used to investigate the phase space density sources. Our simulation results and theoretical arguments suggest that drift shell splitting changes the phase space location of the source to smaller L shells, which typically reduces outer zone phase space density enhancements, and this reduction has a limit corresponding to two-dimensional local diffusion on a curved surface in the phase space.