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Authors: Vernov S N, Gorchakov E V, Kuznetsov S N, Logachev Yu. I, Sosnovets E N, et al.
Title: Particle fluxes in the outer geomagnetic field
Abstract: The outer geomagnetic field comprises the outer radiation belt, consisting of electrons with energies of 104–107 ev, and the unstable radiation zone. The outer radiation belt is bounded on its inner side by a gap, which is at various times located at a distance of 2.2–3.5 RE and in which a considerable precipitation of electrons from radiation belts occurs, possibly owing to a high intensity of electromagnetic waves. The boundary separating the outer radiation belt from the unstable radiation zone is at λ ∼ 71° and ∼9 RE in the equatorial plane on the sunlit side, and at 7–8 RE in the equatorial plane on the nightside. Beyond this, the unstable radiation zone extends out to the magnetosphere boundary and up to λ ∼ 77° on the sunlit side, and out to 14–15 RE on the nightsi. . .
Date: 02/1969 Publisher: Reviews of Geophysics Pages: 257-280 DOI: 10.1029/RG007i001p00257 Available at: http://onlinelibrary.wiley.com/doi/10.1029/RG007i001p00257/abstract
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Authors: Vasko I. Y., Agapitov O. V., Mozer F S, Artemyev A. V., Drake J. F., et al.
Title: Electron holes in the outer radiation belt: Characteristics and their role in electron energization
Abstract: Van Allen Probes have detected electron holes (EHs) around injection fronts in the outer radiation belt. Presumably generated near equator, EHs propagate to higher latitudes potentially resulting in energization of electrons trapped within EHs. This process has been recently shown to provide electrons with energies up to several tens of keV and requires EH propagation up to rather high latitudes. We have analyzed more than 100 EHs observed around a particular injection to determine their kinetic structure and potential energy sources supporting the energization of trapped electrons. EHs propagate with velocities from 1000 to 20,000 km/s (a few times larger than the thermal velocity of the coldest background electron population). The parallel scale of observed EHs is from 0.3 to 3 km that i. . .
Date: 12/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023083 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023083/full
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Authors: Vasko I. Y., Agapitov O. V., Mozer F S, and Artemyev A. V.
Title: Thermal electron acceleration by electric field spikes in the outer radiation belt: Generation of field-aligned pitch angle distributions
Abstract: Van Allen Probes observations in the outer radiation belt have demonstrated an abundance of electrostatic electron-acoustic double layers (DL). DLs are frequently accompanied by field-aligned (bidirectional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV. We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e., due to reflections from DL potential humps. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi me. . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021644 Available at: http://doi.wiley.com/10.1002/2015JA021644http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021644
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Authors: Vasko I. Y., Agapitov O. V., Mozer F S, Bonnell J. W., Artemyev A. V., et al.
Title: Electron-acoustic solitons and double layers in the inner magnetosphere
Abstract: The Van Allen Probes observe generally two types of electrostatic solitary waves (ESW) contributing to the broadband electrostatic wave activity in the nightside inner magnetosphere. ESW with symmetric bipolar parallel electric field are electron phase space holes. The nature of ESW with asymmetric bipolar (and almost unipolar) parallel electric field has remained puzzling. To address their nature, we consider a particular event observed by Van Allen Probes to argue that during the broadband wave activity electrons with energy above 200 eV provide the dominant contribution to the total electron density, while the density of cold electrons (below a few eV) is less than a few tenths of the total electron density. We show that velocities of the asymmetric ESW are close to velocity of electron. . .
Date: 05/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074026 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL074026/full
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Authors: Vasko I. Y., Agapitov O. V., Mozer F, Artemyev A. V., and Jovanovic D.
Title: Magnetic field depression within electron holes
Abstract: We analyze electron holes that are spikes of the electrostatic field (up to 500 mV/m) observed by Van Allen Probes in the outer radiation belt. The unexpected feature is the magnetic field depression of about several tens of picotesla within many of the spikes. The earlier observations showed amplification or negligible perturbations of the magnetic field within the electron holes. We suggest that the observed magnetic field depression is due to the diamagnetic current of hot and highly anisotropic population of electrons trapped within the electron holes. The required trapped population should have a density up to 65% of the background plasma density, a temperature up to several keV, and a temperature anisotropy T⊥/T∥∼2. We argue that the observed electron holes could be generated. . .
Date: 04/2015 Publisher: Geophysical Research Letters Pages: 2123 - 2129 DOI: 10.1002/2015GL063370 Available at: http://doi.wiley.com/10.1002/2015GL063370
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Authors: Vasko I. Y., Agapitov O. V., Mozer F S, Artemyev A. V., Krasnoselskikh V. V., et al.
Title: Diffusive scattering of electrons by electron holes around injection fronts
Abstract: Van Allen Probes have detected nonlinear electrostatic spikes around injection fronts in the outer radiation belt. These spikes include electron holes (EH), double layers, and more complicated solitary waves. We show that EHs can efficiently scatter electrons due to their substantial transverse electric fields. Although the electron scattering driven by EHs is diffusive, it cannot be evaluated via the standard quasi-linear theory. We derive analytical formulas describing local electron scattering by a single EH and verify them via test particle simulations. We show that the most efficiently scattered are gyroresonant electrons (crossing EH on a time scale comparable to the local electron gyroperiod). We compute bounce-averaged diffusion coefficients and demonstrate their dependence on the . . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023337 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023337/full
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Authors: Valek P. W., Goldstein J, Jahn J -M, McComas D J, and Spence H E
Title: First joint in situ and global observations of the medium-energy oxygen and hydrogen in the inner magnetosphere
Abstract: We present the first simultaneous observations of the in situ ions and global Energetic Neutral Atom (ENA) images of the composition-separated, medium-energy (~1–50 keV) particle populations of the inner magnetosphere. The ENA emissions are mapped into L shell/magnetic local time space based on the exospheric density along the line of sight (LOS). The ENA measurement can then be scaled to determine an average ion flux along a given LOS. The in situ ion flux tends to be larger than the scaled ENAs at the same local time. This indicates that the ion population is more concentrated in the Van Allen Probes orbital plane than distributed along the Two Wide-angle Imaging Neutral-atom Spectrometers LOS. For the large storm of 14 November 2012, we observe that the concentration of O (in situ i. . .
Date: 09/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 7615 - 7628 DOI: 10.1002/2015JA021151 Available at: http://doi.wiley.com/10.1002/2015JA021151http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021151
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Authors: Vainchtein D., Zhang X.-J., Artemyev A. V., Mourenas D., Angelopoulos V, et al.
Title: Evolution of electron distribution driven by nonlinear resonances with intense field-aligned chorus waves
Abstract: 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 . . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025654 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025654
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