An Empirical Model of the Equatorial Electron Pitch Angle Distributions in Earth's Outer Radiation Belt

An Empirical Model of the Equatorial Electron Pitch Angle Distributions in Earth's Outer Radiation Belt

Abstract 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 fit...

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Bibliographic Details
Main Authors: Artem Smirnov, Yuri Y. Shprits, Hayley Allison, Nikita Aseev, Alexander Drozdov, Peter Kollmann, Dedong Wang, Anthony Saikin
Format: Article
Language:English
Published: Wiley 2022-09-01
Series:Space Weather
Subjects:
pitch angle
radiation belt
model
magnetosphere
van allen probes
electrons
Online Access:https://doi.org/10.1029/2022SW003053
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Summary:Abstract 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.
ISSN:1542-7390

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