Quasi‐linear simulations of inner radiation belt electron pitch angle and energy distributions

Albert, J. M.; Starks, M.; Horne, Richard B.; Meredith, Nigel P.; Glauert, S. A.

doi:10.1002/2016gl067938

Cited by 76 publications

(99 citation statements)

References 48 publications

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“…Mourenas et al () also found MS waves with relatively smaller wave normal angle are more favorable for scattering electrons from the analyses of Quasi‐linear theory (QLT), which is another widely used method to study MS wave‐particle interaction (e.g., Horne et al, ; Ma et al, ). Moreover, the scattering effect is very sensitive to the wave normal angle, which is consistent with the results of Albert () and Albert et al (). The reason for the sensitivity lies in the fact that the resonance velocity v res = ω / k cos φ changes sharply as φ approaches 90°, while the overall phase velocity of ω / k remains almost unchanged.…”

Section: Parametric Studysupporting

confidence: 91%

“…As shown in Figure h, butterfly distribution is produced from the very beginning inside the plasmapause, which means MS waves accelerate and scatter 90° electrons directly. This mechanism has been interpreted as parallel acceleration due to Landau resonance (Li, Ni, et al, ) or, equivalently, the negative cross diffusion coefficients (Albert et al, ). Outside the plasmapause, as shown in Figure i, the MS waves scatter medium pitch angle electrons and produce a slot at around 80° pitch angles in the first few hours.…”

Section: Electron Diffusion Simulationmentioning

confidence: 99%

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The Radiation Belt Electron Scattering by Magnetosonic Wave: Dependence on Key Parameters

Lei

Xie

et al. 2017

JGR Space Physics

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Magnetosonic (MS) waves have been found capable of creating radiation belt electron butterfly distributions in the inner magnetosphere. To investigate the physical nature of the interactions between radiation belt electrons and MS waves, and to explore a preferential condition for MS waves to scatter electrons efficiently, we performed a comprehensive parametric study of MS wave‐electron interactions using test particle simulations. The diffusion coefficients simulated by varying the MS wave frequency show that the scattering effect of MS waves is frequency insensitive at low harmonics (f < 20 fcp), which has great implications on modeling the electron scattering caused by MS waves with harmonic structures. The electron scattering caused by MS waves is very sensitive to wave normal angles, and MS waves with off 90° wave normal angles scatter electrons more efficiently. By simulating the diffusion coefficients and the electron phase space density evolution at different L shells under different plasma environment circumstances, we find that MS waves can readily produce electron butterfly distributions in the inner part of the plasmasphere where the ratio of electron plasma‐to‐gyrofrequency (fpe/fce) is large, while they may essentially form a two‐peak distribution outside the plasmapause and in the inner radiation belt where fpe/fce is small.

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Section: Parametric Studysupporting

confidence: 91%

Section: Electron Diffusion Simulationmentioning

confidence: 99%

The Radiation Belt Electron Scattering by Magnetosonic Wave: Dependence on Key Parameters

Lei

Xie

et al. 2017

JGR Space Physics

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“…Finally, Figures shows the great diversity of solutions obtained according to the choice of models (both D LL and τ ), which argues in favor of more simulations (for different events) to confirm the findings of the current study. The good reproduction of the flux decay with the lifetime of this study gives also confidence in the pitch angle diffusion coefficients and a future capability to simulate finer effects with these coefficients used within a 3‐D Fokker‐Planck framework [e.g., Tu et al , ; Drozdov et al , ], such as, for instance, the formation of butterfly pitch angle distributions distribution [ Zhao et al , , ; Albert et al , ] and pitch angle dependent loss [e.g., Yu et al , ].…”

Section: Validation With Van Allen Probes Observationsmentioning

confidence: 80%

Effects of whistler mode hiss waves in March 2013

et al. 2017

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We present simulations of the loss of radiation belt electrons by resonant pitch angle diffusion caused by whistler mode hiss waves for March 2013. Pitch angle diffusion coefficients are computed from the wave properties and the ambient plasma data obtained by the Van Allen Probes with a resolution of 8 h and 0.1 L shell. Loss rates follow a complex dynamic structure, imposed by the wave and plasma properties. Hiss effects can be strong, with minimum lifetimes (of ~1 day) moving from energies of ~100 keV at L ~ 5 up to ~2 MeV at L ~ 2 and stop abruptly, similarly to the observed energy‐dependent inner belt edge. Periods when the plasmasphere extends beyond L ~ 5 favor long‐lasting hiss losses from the outer belt. Such loss rates are embedded in a reduced Fokker‐Planck code and validated against Magnetic Electron and Ion Spectrometer observations of the belts at all energy. Results are complemented with a sensitivity study involving different radial diffusion and lifetime models. Validation is carried out globally at all L shells and energies. The good agreement between simulations and observations demonstrates that hiss waves drive the slot formation during quiet times. Combined with transport, they sculpt the energy structure of the outer belt into an “S shape.” Low energy electrons (<0.3 MeV) are less subject to hiss scattering below L = 4. In contrast, 0.3–1.5 MeV electrons evolve in an environment that depopulates them as they migrate from L ~ 5 to L ~ 2.5. Ultrarelativistic electrons are not affected by hiss losses until L ~ 2–3.

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“…Hiss waves interact with tens to hundreds of keV electrons, causing electron pitch angle scattering and precipitation of Earth's radiation belt electrons into the upper atmosphere [Abel and Thorne, 1998;Horne and Thorne, 1998;Shprits et al, 2008;Ni et al, 2013Ni et al, , 2014]. In addition, Landau resonance due to hiss waves affects the energetic electrons at high pitch angles (close to 90°) or at energies slightly lower than the electron cyclotron resonance energy, which may contribute to the formation of "butterfly" pitch angle distribution in the inner radiation belt [Albert et al, 2016]. The pitch angle scattering due to the combined effect of cyclotron and Landau resonance effects leads to the typical "top-hat"-shaped pitch angle distribution of tens to hundreds of keV electrons and the flattened pitch angle distribution at higher energies up to several MeV in the outer radiation belt [Ni et al, 2013].…”

Section: Introductionmentioning

confidence: 99%

Characteristic energy range of electron scattering due to plasmaspheric hiss

Thorne

et al. 2016

JGR Space Physics

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We investigate the characteristic energy range of electron flux decay due to the interaction with plasmaspheric hiss in the Earth's inner magnetosphere. The Van Allen Probes have measured the energetic electron flux decay profiles in the Earth's outer radiation belt during a quiet period following the geomagnetic storm that occurred on 7 November 2015. The observed energy of significant electron decay increases with decreasing L shell and is well correlated with the energy band corresponding to the first adiabatic invariant μ = 4–200 MeV/G. The electron diffusion coefficients due to hiss scattering are calculated at L = 2–6, and the modeled energy band of effective pitch angle scattering is also well correlated with the constant μ lines and is consistent with the observed energy range of electron decay. Using the previously developed statistical plasmaspheric hiss model during modestly disturbed periods, we perform a 2‐D Fokker‐Planck simulation of the electron phase space density evolution at L = 3.5 and demonstrate that plasmaspheric hiss causes the significant decay of 100 keV–1 MeV electrons with the largest decay rate occurring at around 340 keV, forming anisotropic pitch angle distributions at lower energies and more flattened distributions at higher energies. Our study provides reasonable estimates of the electron populations that can be most significantly affected by plasmaspheric hiss and the consequent electron decay profiles.

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Quasi‐linear simulations of inner radiation belt electron pitch angle and energy distributions

Cited by 76 publications

References 48 publications

The Radiation Belt Electron Scattering by Magnetosonic Wave: Dependence on Key Parameters

The Radiation Belt Electron Scattering by Magnetosonic Wave: Dependence on Key Parameters

Effects of whistler mode hiss waves in March 2013

Characteristic energy range of electron scattering due to plasmaspheric hiss

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