Open AccessAn Empirical Model of the Equatorial Electron Pitch Angle Distributions in Earth's Outer Radiation Belt
Author(s) -
Smirnov Artem,
Shprits Yuri Y.,
Allison Hayley,
Aseev Nikita,
Drozdov Alexander,
Kollmann Peter,
Wang Dedong,
Saikin Anthony
Publication year - 2022
Publication title -
space weather
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.254
H-Index - 56
ISSN - 1542-7390
DOI - 10.1029/2022sw003053
Subject(s) - van allen radiation belt , physics , computational physics , electron spectrometer , electron , pitch angle , earth's magnetic field , van allen probes , flux (metallurgy) , magnetosphere , geophysics , plasma , magnetic field , cathode ray , materials science , quantum mechanics , metallurgy
In this study, we present an empirical model of the equatorial electron pitch angle distributions (PADs) in the outer radiation belt based on the full data set collected by the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard the Van Allen Probes in 2012–2019. The PADs are fitted with a combination of the first, third and fifth sine harmonics. The resulting equation resolves all PAD types found in the outer radiation belt (pancake, flat‐top, butterfly and cap PADs) and can be analytically integrated to derive omnidirectional flux. We introduce a two‐step modeling procedure that for the first time ensures a continuous dependence on L, magnetic local time and activity, parametrized by the solar wind dynamic pressure. We propose two methods to reconstruct equatorial electron flux using the model. The first approach requires two uni‐directional flux observations and is applicable to low‐PA data. The second method can be used to reconstruct the full equatorial PADs from a single uni‐ or omnidirectional measurement at off‐equatorial latitudes. The model can be used for converting the long‐term data sets of electron fluxes to phase space density in terms of adiabatic invariants, for physics‐based modeling in the form of boundary conditions, and for data assimilation purposes.