Sensitivity of EMIC Wave-Driven Scattering Loss of Ring Current Protons to Wave Normal Angle Distribution

TitleSensitivity of EMIC Wave-Driven Scattering Loss of Ring Current Protons to Wave Normal Angle Distribution
Publication TypeJournal Article
Year of Publication2019
AuthorsCao, X, Ni, B, Summers, D, Shprits, YY, Gu, X, Fu, S, Lou, Y, Zhang, Y, Ma, X, Zhang, W, Huang, H, Yi, J
JournalGeophysical Research Letters
Pagination590 - 598
Date Published01/2019
KeywordsEMIC waves; Quasi‐linear diffusion; Ring current protons; Van Allen Probes; wave‐particle interactions
AbstractElectromagnetic ion cyclotron waves have long been recognized to play a crucial role in the dynamic loss of ring current protons. While the field‐aligned propagation approximation of electromagnetic ion cyclotron waves was widely used to quantify the scattering loss of ring current protons, in this study, we find that the wave normal distribution strongly affects the pitch angle scattering efficiency of protons. Increase of peak normal angle or angular width can considerably reduce the scattering rates of ≤10 keV protons. For >10 keV protons, the field‐aligned propagation approximation results in a pronounced underestimate of the scattering of intermediate equatorial pitch angle protons and overestimates the scattering of high equatorial pitch angle protons by orders of magnitude. Our results suggest that the wave normal distribution of electromagnetic ion cyclotron waves plays an important role in the pitch angle evolution and scattering loss of ring current protons and should be incorporated in future global modeling of ring current dynamics.
URLhttps://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL081550
DOI10.1029/2018GL081550
Short TitleGeophys. Res. Lett.


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