Survey of radiation belt energetic electron pitch angle distributions based on the Van Allen Probes MagEIS measurements

Shi, Run; Summers, Danny; Ni, Binbin; Fennell, J. F.; Blake, J. B.; Spence, H. E.; Reeves, G. D.

doi:10.1002/2015ja021724

Cited by 28 publications

(43 citation statements)

References 73 publications

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“…We assume an initial pitch angle distribution of

f = f_{0} false(E, L false) \sin^{3} false(α false)

. The equatorially mirroring electron flux is calculated from the empirical electron model environment AE‐8 (Vette, ), f 0 ( E , L ), and the exponent is chosen considering Shi et al () who performed a survey on electron pitch angle distributions using Van Allen Probes MagEIS measurements.…”

Section: Methodsmentioning

confidence: 99%

Effects of VLF Transmitter Waves on the Inner Belt and Slot Region

et al. 2019

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Signals from very low frequency (VLF) transmitters can leak from the Earth‐ionosphere wave guide into the inner magnetosphere, where they propagate in the whistler mode and contribute to electron dynamics in the inner radiation belt and slot region. Observations show that the waves from each VLF transmitter are highly localized, peaking on the nightside in the vicinity of the transmitter. In this study we use ∼5 years of Van Allen Probes observations to construct global statistical models of the bounce‐averaged pitch angle diffusion coefficients for each individual VLF transmitter, as a function of L*, magnetic local time (MLT), and geographic longitude. We construct a 1‐D pitch angle diffusion model with implicit longitude and MLT dependence to show that VLF transmitter waves weakly scatter electrons into the drift loss cone. We find that global averages of the wave power, determined by averaging the wave power over MLT and longitude, capture the long‐term dynamics of the loss process, despite the highly localized nature of the waves in space. We use our new model to assess the role of VLF transmitter waves, hiss waves, and Coulomb collisions on electron loss in the inner radiation belt and slot region. At moderate relativistic energies, E∼500 keV, waves from VLF transmitters reduce electron lifetimes by an order of magnitude or more, down to the order of 200 days near the outer edge of the inner radiation belt. However, VLF transmitter waves are ineffective at removing multi–megaelectron volt electrons from either the inner radiation belt or slot region.

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“…We assume an initial pitch angle distribution of

f = f_{0} false(E, L false) \sin^{3} false(α false)

Section: Methodsmentioning

confidence: 99%

Effects of VLF Transmitter Waves on the Inner Belt and Slot Region

et al. 2019

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“…Precomputed empirical models for electron pitch angle distribution can be useful for initial and boundary conditions, analytical estimates, etc. PSD models are legion in the literature (e.g., Vampola, ; Horne, Meredith, et al, ; Gannon et al, ; Xudong et al, ; Zhao et al, , ; Chen et al, ; Ni et al, ; Shi et al, ; Allison et al, , ). For instance, Denton et al (2015, Denton et al, ) derived an empirical model of particle fluxes in the energy range ~1 eV to ~40 keV at geosynchronous orbit based on a total of 82 satellite years of observations (between 1990 and 2007) made by LANL/GEO data.…”

Section: New Radiation Belt Modeling Capabilities and The Quantificatmentioning

confidence: 99%

Particle Dynamics in the Earth's Radiation Belts: Review of Current Research and Open Questions

et al. 2020

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The past decade transformed our observational understanding of energetic particle processes in near‐Earth space. An unprecedented suite of observational systems was in operation including the Van Allen Probes, Arase, Magnetospheric Multiscale, Time History of Events and Macroscale Interactions during Substorms, Cluster, GPS, GOES, and Los Alamos National Laboratory‐GEO magnetospheric missions. They were supported by conjugate low‐altitude measurements on spacecraft, balloons, and ground‐based arrays. Together, these significantly improved our ability to determine and quantify the mechanisms that control the buildup and subsequent variability of energetic particle intensities in the inner magnetosphere. The high‐quality data from National Aeronautics and Space Administration's Van Allen Probes are the most comprehensive in situ measurements ever taken in the near‐Earth space radiation environment. These observations, coupled with recent advances in radiation belt theory and modeling, including dramatic increases in computational power, have ushered in a new era, perhaps a “golden era,” in radiation belt research. We have edited a Journal of Geophysical Research: Space Science Special Collection dedicated to Particle Dynamics in the Earth's Radiation Belts in which we gather the most recent scientific findings and understanding of this important region of geospace. This collection includes the results presented at the American Geophysical Union Chapman International Conference in Cascais, Portugal (March 2018) and many other recent and relevant contributions. The present article introduces and review the context, current research, and main questions that motivate modern radiation belt research divided into the following topics: (1) particle acceleration and transport, (2) particle loss, (3) the role of nonlinear processes, (4) new radiation belt modeling capabilities and the quantification of model uncertainties, and (5) laboratory plasma experiments.

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“…They found that the occurrence rate of butterfly PADs is highest (~80%) at ~20–04 magnetic local time (MLT) at L > ~5.5, while ~50% occurrence rate of butterfly PADs is also observed at 11–15 MLT at L ~ 4, and the outer belt butterfly PADs do not show significant correlation with the solar wind dynamic pressure. Some studies have also focused on electron PADs in the slot region and inner belt (e.g., Lyons & Williams, , ; Shi et al, ; Zhao et al, , ). Lyons and Williams (, ), using 35‐ to 560‐keV electron data from Explorer 45, studied both quiet time and storm time structures of radiation belt electron PADs at 1.7 < L < 5.2.…”

Section: Introductionmentioning

confidence: 99%

“…They also showed that for ~460‐keV electrons, 90°‐minimum PADs are generally present in the inner belt and appear in the slot region during quiet times, normal PADs dominate at L ~ 3.5–4, and cap PADs generally appear in the slot region at the decay phase of storms and are likely caused by plasmaspheric hiss wave scattering. Shi et al (), using data from MagEIS instruments, performed a statistical survey of radiation belt electron PADs and their correlation with electron energy, MLT, geomagnetic Kp index, and L‐shell. They found that the electron PADs are more exceedingly peaked at 90° PA in the low L region, during active times, on the dayside, and for higher‐energy electrons.…”

Section: Introductionmentioning

confidence: 99%

An Empirical Model of Radiation Belt Electron Pitch Angle Distributions Based On Van Allen Probes Measurements

et al. 2018

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Based on over 4 years of Van Allen Probes measurements, an empirical model of radiation belt electron equatorial pitch angle distribution (PAD) is constructed. The model, developed by fitting electron PADs with Legendre polynomials, provides the statistical PADs as a function of L-shell (L = 1-6), magnetic local time, electron energy (~30 keV to 5.2 MeV), and geomagnetic activity (represented by the Dst index) and is also the first empirical PAD model in the inner belt and slot region. For megaelectron volt electrons, model results show more significant day-night PAD asymmetry of electrons with higher energies and during disturbed times, which is caused by geomagnetic field configuration and flux radial gradient changes. Steeper PADs with higher fluxes around 90°pitch angle and lower fluxes at lower pitch angles for higherenergy electrons and during active times are also present, which could be due to electromagnetic ion cyclotron wave scattering. For hundreds of kiloelectron volt electrons, cap PADs are generally present in the slot region during quiet times and their energy-dependent features are consistent with hiss wave scattering, while during active times, cap PADs are less significant especially at outer part of slot region, which could be due to the complex energizing and transport processes. The 90°-minimum PADs are persistently present in the inner belt and appear in the slot region during active times, and minima at 90°pitch angle are more significant for electrons with higher energies, which could be a critical evidence in identifying the underlying physical processes responsible for the formation of 90°-minimum PADs.

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Survey of radiation belt energetic electron pitch angle distributions based on the Van Allen Probes MagEIS measurements

Cited by 28 publications

References 73 publications

Effects of VLF Transmitter Waves on the Inner Belt and Slot Region

Effects of VLF Transmitter Waves on the Inner Belt and Slot Region

Particle Dynamics in the Earth's Radiation Belts: Review of Current Research and Open Questions

An Empirical Model of Radiation Belt Electron Pitch Angle Distributions Based On Van Allen Probes Measurements

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