Diffusive Transport of Several Hundred keV Electrons in the Earth's Slot Region

Ma, Q.; Li, W.; Thorne, R. M.; Bortnik, J.; Reeves, G. D.; Turner, D. L.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Baker, D. N.

doi:10.1002/2017ja024452

Cited by 16 publications

(12 citation statements)

References 83 publications

(123 reference statements)

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“…With a full Fokker‐Planck code, one can solve today simultaneously the following processes: radial diffusion, pitch angle diffusion, energy diffusion, cross energy and pitch angle diffusion, Coulomb collision, and anomalous diffusion. Among the most well‐established Fokker‐Planck codes are the ONERA Salammbô code (e.g., Beutier & Boscher, ; Bourdarie et al, , , ; Pugacheva et al, ; Beutier et al, 2005; Varotsou et al, , ; Maget et al, ; Herrera et al, ), the British Antarctic Survey (BAS) Radiation Belt Code (e.g., Glauert et al, , ; Glauert & Horne, ; Horne et al, ; Meredith et al, , ), the VERB 3‐D code (e.g., Subbotin & Shprits, ; Shprits et al, ; Subbotin et al, , ; Kim et al, 2011, Kim et al, ; Drozdov et al, ) recently extended to a 4‐D version (e.g., Aseev et al, ; Shprits et al, ) to soon incorporate models of nonlinear wave‐particle interactions, the University of California, Los Angeles (UCLA) 3‐D diffusion code (e.g., Tao et al, ; Li et al, ; Li, Ma, et al, ; Ma et al, , , , Ma et al, that incorporates the (UCLA) Full Diffusion Code (e.g., Ni et al, 2008, Ni et al, ; Shprits & Ni, 2009) in order to compute diffusion coefficients (similarly to VERB 3‐D/4‐D), the radiation belt code of the Space Vehicles Directorate of the U.S. Air Force Research Laboratory (AFRL) (e.g., Albert, , ; Albert et al, ; Albert & Young, ; Selesnick, Albert, & Starks, ), the LANL Dynamic Radiation Environment Assimilation Model (DREAM) 1‐D (e.g., Tu et al, 2009; Reeves et al, ; Welling et al, ) and 3‐D codes (Camporeale et al, , ; Cunningham, ; Cunningham et al, ; Tu et al, ), the Commissariat à l'Energie Atomique (CEA) CEVA code (Réveillé, ; Ripoll & Mourenas, 2012; Ripoll, Chen, et al, , Ripoll, Reeves, et al, , Ripoll et al, , ), and the STEERB code developed in China (e.g., Su et al, …”

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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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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“…Figure 8 shows that the typical time scale of the evolution of the electron distribution via nonlinear trapping and scattering by long and intense chorus wave-packets can be about half an hour, i.e., rather short compared with ∼ 4 − 10 hours typically for quasi-linear diffusion by the bulk of lower-intensity chorus waves [e.g., Mourenas et al, 2014;Li et al, 2016;Ma et al, 2017b;Yang et al, 2018]. Although such fast electron flux variations have been occasionally observed [e.g., Agapitov et al, 2015a;Foster et al, 2017], they are rather unusual.…”

Section: Time Scale Of Electron Distribution Evolutionmentioning

confidence: 99%

Evolution of Electron Distribution Driven by Nonlinear Resonances With Intense Field‐Aligned Chorus Waves

et al. 2018

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Resonant electron interaction with whistler mode chorus waves is recognized as one of the main drivers of radiation belt dynamics. For moderate wave intensity, this interaction is well described by quasi-linear theory. However, recent statistics of parallel propagating chorus waves have demonstrated that 5-20% of the observed waves are sufficiently intense to interact nonlinearly with electrons. Such interactions include phase trapping and phase bunching (nonlinear scattering) effects not described by quasi-linear diffusion. For sufficiently long (large) wave packets, these nonlinear effects can result in very rapid electron acceleration and scattering. In this paper we introduce a method to include trapping and nonlinear scattering into the kinetic equation describing the evolution of the electron distribution function. We use statistics of Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms observations to determine the probability distribution of intense, long wave packets as a function of power and frequency. Then we develop an analytical model of individual particle resonance with an intense chorus wave packet and derive the main properties of this interaction: probability of electron trapping, energy change due to trapping and nonlinear scattering. These properties are combined in a nonlocal operator acting on the electron distribution function. When multiple waves are present, we average the obtained operator over the observed distributions of waves and examine solutions of the resultant kinetic equation. We also examine energy conservation and its implications in systems with nonlinear wave-particle interaction. Key Points: • We propose a model of electron nonlinear resonant interaction with long and intense chorus wave packets • We derive a new generalized kinetic equation for electrons that encompasses nonlinear interactions with long chorus wave packets • Nonlinear interactions with long wave packets can produce rapid electron acceleration for observed wave characteristics

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“…At ~18:20 UT, the seed population enhancements appeared at L* = 3.9 and MLT = 5.8. Using a 3‐D diffusion model, Ma et al () have simulated the observed 10‐day diffusive evolution of energetic electrons in the slot region. In this event, ULF waves were observed at ~18:20 UT by Van Allen Probe B.…”

Section: Discussionmentioning

confidence: 99%

Rapid Enhancements of the Seed Populations in the Heart of the Earth's Outer Radiation Belt: A Multicase Study

Tang

Xie

et al. 2018

JGR Space Physics

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To better understand rapid enhancements of the seed populations (hundreds of keV electrons) in the heart of the Earth's outer radiation belt (L*~3.5-5.0) during different geomagnetic activities, we investigate three enhancement events measured by Van Allen Probes in detail. Observations of the fluxes and the pitch angle distributions of energetic electrons are analyzed to determine rapid enhancements of the seed populations. Our study shows that three specified processes associated with substorm electron injections can lead to rapid enhancements of the seed populations, and the electron energy increases up to 342 keV. In the first process, substorm electron injections accompanied by the transient and intense substorm electric fields can directly lead to rapid enhancements of the seed populations in the heart of the outer radiation belt. In the second process, the substorm injected electrons are first trapped in the outer radiation belt and subsequently transported into L* < 4.5 by the convection electric field. In the third process, the lower energy electrons are first injected at L*~5.3 and then undergo drift resonance with ultralow-frequency waves. These accelerated electrons by ultralow-frequency waves are further transported into L* < 4.5 due to the convection electric field. This process is consistent with the radial diffusion. Our results suggest that these specified processes are important for understanding the dynamics of the seed populations in the heart of the outer radiation belt. TANG ET AL. 4895

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Diffusive Transport of Several Hundred keV Electrons in the Earth's Slot Region

Cited by 16 publications

References 83 publications

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

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

Evolution of Electron Distribution Driven by Nonlinear Resonances With Intense Field‐Aligned Chorus Waves

Rapid Enhancements of the Seed Populations in the Heart of the Earth's Outer Radiation Belt: A Multicase Study

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