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2019
Authors: Yuan Zhigang, Yao Fei, Yu Xiongdong, Huang Shiyong, and Ouyang Zhihai
Title: An Automatic Detection Algorithm Applied to Fast Magnetosonic Waves With Observations of the Van Allen Probes
Abstract: Fast magnetosonic (MS) waves can play an important role in the evolution of the inner magnetosphere. However, there is still not an effective method to quantitatively identify such waves for observations of the Van Allen Probes reasonably. In this paper, we used Van Allen Probes data from 18 September 2012 to 30 September 2014 to find a more comprehensive automatic detection algorithm for fast MS waves through statistical analysis of the major properties, including the planarity, ellipticity, and wave normal angle of whole fluctuations using the singular value decomposition method. According to a control variate method, we find an obvious difference between fast MS waves and other waves in the statistical distribution of their major properties. After eliminating the influence of background. . .
Date: Apr-05-2021 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026387 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026387
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Authors: Omura Yoshiharu, Hsieh Yi‐Kai, Foster John C., Erickson Philip J., Kletzing Craig A., et al.
Title: Cyclotron Acceleration of Relativistic Electrons Through Landau Resonance With Obliquely Propagating Whistler‐Mode Chorus Emissions
Abstract: Efficient acceleration of relativistic electrons at Landau resonance with obliquely propagating whistler‐mode chorus emissions is confirmed by theory, simulation, and observation. The acceleration is due to the perpendicular component of the wave electric field. We first review theoretical analysis of nonlinear motion of resonant electrons interacting with obliquely propagating whistler‐mode chorus. We have derived formulae of inhomogeneity factors for Landau and cyclotron resonances to analyze nonlinear wave trapping of energetic electrons by an obliquely propagating chorus element. We performed test particle simulations to confirm that nonlinear wave trapping by both Landau and cyclotron resonances can take place for a wide range of energies. For an element of large amplitude chorus . . .
Date: 04/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026374 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026374
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Authors: Omura Yoshiharu, Hsieh Yi‐Kai, Foster John C., Erickson Philip J., Kletzing Craig A., et al.
Title: Cyclotron Acceleration of Relativistic Electrons Through Landau Resonance With Obliquely Propagating Whistler‐Mode Chorus Emissions
Abstract: Efficient acceleration of relativistic electrons at Landau resonance with obliquely propagating whistler‐mode chorus emissions is confirmed by theory, simulation, and observation. The acceleration is due to the perpendicular component of the wave electric field. We first review theoretical analysis of nonlinear motion of resonant electrons interacting with obliquely propagating whistler‐mode chorus. We have derived formulae of inhomogeneity factors for Landau and cyclotron resonances to analyze nonlinear wave trapping of energetic electrons by an obliquely propagating chorus element. We performed test particle simulations to confirm that nonlinear wave trapping by both Landau and cyclotron resonances can take place for a wide range of energies. For an element of large amplitude chorus . . .
Date: 04/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026374 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026374
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Authors: Juhász Lilla, Omura Yoshiharu, Lichtenberger János, and Friedel Reinhard H.
Title: Evaluation of Plasma Properties From Chorus Waves Observed at the Generation Region
Abstract: In this study we present an inversion method which provides thermal plasma population parameters from characteristics of chorus emissions only. Our ultimate goal is to apply this method to ground‐based data in order to derive the lower‐energy boundary condition for many radiation belt models. The first step is to test the chorus inversion method on in situ data of the Van Allen Probes in the generation region. The density and thermal velocity of energetic electrons (few kiloelectron volts to 100 keV) are derived from frequency sweep rate and starting frequencies of chorus emissions through analysis of wave data from the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes. The nonlinear wave growth theory of Omura and Nunn (2011, https://doi. . .
Date: 05/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026337 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026337
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Authors: Yu Xiongdong, Yuan Zhigang, Huang Shiyong, Yao Fei, Qiao Zheng, et al.
Title: Excitation of extremely low-frequency chorus emissions: The role of background plasma density
Abstract: Low‐frequency chorus emissions have recently attracted much attention due to the suggestion that they may play important roles in the dynamics of the Van Allen Belts. However, the mechanism (s) generating these low‐frequency chorus emissions have not been well understood. . In this letter, we report an interesting case in which background plasma density lowered the lower cutoff frequency of chorus emissions from above 0.1 f ce (typical ordinary chorus) to 0.02 f ce (extremely low‐frequency chorus). Those extremely low‐frequency chorus waves were observed in a rather dense plasma, where the number density N e was found to be several times larger than has been associated with observations of ordinary chorus waves. For suprathermal electrons whose free energy is supplied by anisotropi. . .
Date: 02/2019 Publisher: Earth and Planetary Physics Pages: 1 - 7 DOI: 10.26464/epp2019001 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.26464/epp2019001
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Authors: Chen Yaru, Zhou Qinghua, He Yihua, Yang Chang, Liu Si, et al.
Title: Global occurrences of electrostatic electron cyclotron harmonic waves associated with radiation belt electron distributions
Abstract: Electrostatic electron cyclotron harmonic (ECH) waves can yield diffuse aurora primarily at higher L‐shells by driving efficient precipitation loss of plasma sheet electrons. Here using the Van Allen Probes high resolution data, we examine in detail the global occurrences of ECH waves during the period from October 1, 2012 to June 30, 2017 and find that there are totally 419 events of enhanced ECH waves. The statistical results demonstrate that ECH waves can be present over a broad region of L=4‐6 and 00‐24 MLT, with a higher occurrence in the region of L=5‐6 and 06‐19 MLT. The electron phase space density exhibits a distinct ring distribution (∂f/∂v⊥ >0) with the peak energy around a few keV. Both ECH wave events and the electron ring distributions are closely related and . . .
Date: 04/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082668 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082668
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Authors: Ripoll J.‐F., Farges T., Lay E. H., and Cunningham G. S.
Title: Local and Statistical Maps of Lightning‐Generated Wave Power Density Estimated at the Van Allen Probes Footprints From the World‐Wide Lightning Location Network Database
Abstract: We propose a new method that uses the World‐Wide Lightning Location Network (WWLLN) to estimate both the local and the drift lightning power density at the Van Allen Probes footprints during 4.3 years (~2 × 108 strokes.). The ratio of the drift power density to the local power density defines a time‐resolved WWLLN‐based model of lightning‐generated wave (LGW) power density ratio, RWWLLN. RWWLLNis computed every ~34 s. This ratio multiplied by the time‐resolved LGW intensity measured by the Probes allows direct computation of pitch angle diffusion coefficients used in radiation belt codes. Statistical analysis shows the median power density ratio is urn:x-wiley:00948276:media:grl58808:grl58808-math-0001 over the Americas. Elsewhere, urn:x-wiley:00948276:media:grl58808:grl58808-ma. . .
Date: 03/2019 Publisher: Geophysical Research Letters Pages: 4122 - 4133 DOI: 10.1029/2018GL081146 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL081146
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Authors: Zhang X.‐J., Mourenas D., Artemyev A. V., Angelopoulos V, Bortnik J, et al.
Title: Nonlinear Electron Interaction With Intense Chorus Waves: Statistics of Occurrence Rates
Abstract: A comprehensive statistical analysis on 8 years of lower‐band chorus wave packets measured by the Van Allen Probes and THEMIS spacecraft is performed to examine whether, when, and where these waves are above the theoretical threshold for nonlinear resonant wave‐particle interaction. We find that ∼5–30% of all chorus waves interact nonlinearly with ∼30‐ to 300‐keV electrons possessing equatorial pitch angles of >40° in the outer radiation belt, especially during disturbed (AE>500 nT) periods with energetic particles associated with injections from the plasma sheet. Such considerable occurrence rates of nonlinear interactions imply that the evolution of energetic electron fluxes should be dominated by nonlinear effects, rather than by quasi‐linear diffusion as commonly assum. . .
Date: 06/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL083833 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083833
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Authors: Shi Run, Li Wen, Ma Qianli, Green Alex, Kletzing Craig A., et al.
Title: Properties of Whistler Mode Waves in Earth's Plasmasphere and Plumes
Abstract: Whistler mode wave properties inside the plasmasphere and plumes are systematically investigated using 5‐year data from Van Allen Probes. The occurrence and intensity of whistler mode waves in the plasmasphere and plumes exhibit dependences on magnetic local time, L, and AE. Based on the dependence of the wave normal angle and Poynting flux direction on L shell and normalized wave frequency to electron cyclotron frequency (fce), whistler mode waves are categorized into four types. Type I: ~0.5 fce with oblique wave normal angles mostly in plumes; Type II: 0.01–0.5 fce with small wave normal angles in the outer plasmasphere or inside plumes; Type III: <0.01 fce with oblique wave normal angles mostly within the plasmasphere or plumes; Type IV: 0.05–0.5 fce with oblique wave normal angl. . .
Date: 01/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026041 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026041
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Authors: Li W, Shen X.‐C., Ma Q, Capannolo L., Shi R., et al.
Title: Quantification of Energetic Electron Precipitation Driven by Plume Whistler Mode Waves, Plasmaspheric Hiss, and Exohiss
Abstract: Whistler mode waves are important for precipitating energetic electrons into Earth's upper atmosphere, while the quantitative effect of each type of whistler mode wave on electron precipitation is not well understood. In this letter, we evaluate energetic electron precipitation driven by three types of whistler mode waves: plume whistler mode waves, plasmaspheric hiss, and exohiss observed outside the plasmapause. By quantitatively analyzing three conjunction events between Van Allen Probes and POES/MetOp satellites, together with quasi‐linear calculation, we found that plume whistler mode waves are most effective in pitch angle scattering loss, particularly for the electrons from tens to hundreds of keV. Our new finding provides the first direct evidence of effective pitch angle scatter. . .
Date: 03/2019 Publisher: Geophysical Research Letters Pages: 3615 - 3624 DOI: 10.1029/2019GL082095 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082095
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Authors: Dai Guyue, Su Zhenpeng, Liu Nigang, Wang Bin, Zheng Huinan, et al.
Title: Quenching of Equatorial Magnetosonic Waves by Substorm Proton Injections
Abstract: Near equatorial (fast) magnetosonic waves, characterized by high magnetic compressibility, are whistler‐mode emissions destabilized by proton shell/ring distributions. In the past, substorm proton injections are widely known to intensify magnetosonic waves in the inner magnetosphere. Here we report the unexpected observations by the Van Allen Probes of the magnetosonic wave quenching associated with the substorm proton injections under both high‐ and low‐density conditions. The enhanced proton thermal pressure distorted the background magnetic field configuration and the cold plasma density distribution. The reduced phase velocities locally allowed the weak growth or even damping of magnetosonic waves. Meanwhile, the spatially irregularly varying refractive indices might suppress the. . .
Date: 05/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082944 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082944
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Authors: Turner D. L., Kilpua E. K. J., Hietala H., Claudepierre S G, O'Brien T P, et al.
Title: The Response of Earth's Electron Radiation Belts to Geomagnetic Storms: Statistics From the Van Allen Probes Era Including Effects From Different Storm Drivers
Abstract: A statistical study was conducted of Earth's radiation belt electron response to geomagnetic storms using NASA's Van Allen Probes mission. Data for electrons with energies ranging from 30 keV to 6.3 MeV were included and examined as a function of L‐shell, energy, and epoch time during 110 storms with SYM‐H ≤−50 nT during September 2012 to September 2017 (inclusive). The radiation belt response revealed clear energy and L‐shell dependencies, with tens of keV electrons enhanced at all L‐shells (2.5 ≤ L ≤ 6) in all storms during the storm commencement and main phase and then quickly decaying away during the early recovery phase, low hundreds of keV electrons enhanced at lower L‐shells (~3 ≤ L ≤ ~4) in upward of 90% of all storms and then decaying gradually during the rec. . .
Date: 01/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026066 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026066
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Authors: Cao Xing, Ni Binbin, Summers Danny, Shprits Yuri Y, Gu Xudong, et al.
Title: Sensitivity of EMIC Wave-Driven Scattering Loss of Ring Current Protons to Wave Normal Angle Distribution
Abstract: Electromagnetic ion cyclotron waves have long been recognized to play a crucial role in the dynamic loss of ring current protons. While the field‐aligned propagation approximation of electromagnetic ion cyclotron waves was widely used to quantify the scattering loss of ring current protons, in this study, we find that the wave normal distribution strongly affects the pitch angle scattering efficiency of protons. Increase of peak normal angle or angular width can considerably reduce the scattering rates of ≤10 keV protons. For >10 keV protons, the field‐aligned propagation approximation results in a pronounced underestimate of the scattering of intermediate equatorial pitch angle protons and overestimates the scattering of high equatorial pitch angle protons by orders of magnitude. Ou. . .
Date: 01/2019 Publisher: Geophysical Research Letters Pages: 590 - 598 DOI: 10.1029/2018GL081550 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL081550
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Authors: Yuan Zhigang, Yu Xiongdong, Ouyang Zhihai, Yao Fei, Huang Shiyong, et al.
Title: Simultaneous trapping of EMIC and MS waves by background plasmas
Abstract: Electromagnetic ion cyclotron waves and fast magnetosonic waves are found to be simultaneously modulated by background plasma density: both kinds of waves were observed in high plasma density regions but vanished in low density regions. Theoretical analysis based on Snell's law and linear growth theory have been utilized to investigate the physical mechanisms driving such modulation. It is suggested that the modulation of fast magnetosonic waves might be due to trapping by plasma density structures, which results from a conservation of the parameter Q during their propagation. Here Q = nrsinψ, with n the refractive index, r the radial distance, and ψ the wave azimuthal angle. As for electromagnetic ion cyclotron waves, the modulation might be owed to the ion composition difference betwee. . .
Date: 02/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026149 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026149
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Authors: Tyler E., Breneman A., Cattell C., Wygant J, Thaller S., et al.
Title: Statistical occurrence and distribution of high amplitude whistler-mode waves in the outer radiation belt
Abstract: We present the first statistical analysis with continuous data coverage and non‐averaged amplitudes of the prevalence and distribution of high‐amplitude (> 5 mV/m) whistler‐mode waves in the outer radiation belt using 5 years of Van Allen Probes data. These waves are most common above L=3.5 and between MLT of 0‐7 where they are present 1‐4% of the time. During high geomagnetic activity, high‐amplitude whistler‐mode wave occurrence rises above 30% in some regions. During these active times the plasmasphere erodes to lower L and high‐amplitude waves are observed at all L outside of it, with the highest occurrence at low L (3.5‐4) in the pre‐dawn sector. These results have important implications for modeling radiation belt particle interactions with chorus, as large‐amp. . .
Date: 02/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082292 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082292
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Authors: Agapitov O., Mourenas D., Artemyev A., Hospodarsky G., and Bonnell J.W.
Title: Timescales for electron quasi‐linear diffusion by lower‐band chorus waves: the effects of ω pe / Ω ce dependence on geomagnetic activity
Abstract: Electron scattering by chorus waves is an important mechanism that can lead to fast electron acceleration and loss in the outer radiation belt. Making use of Van Allen Probes measurements, we present the first statistical survey of megaelectron volt electron pitch angle and energy quasi‐linear diffusion rates by chorus waves as a function of L‐shell, local time, and AE index, taking into account the local electron plasma frequency to gyrofrequency ratio ωpe/Ωce, chorus wave frequency, and resonance wave amplitude. We demonstrate that during disturbed periods, ωpe/Ωce strongly decreases in the night sector, leading to a faster electron loss but also a much faster electron energization in two distinct regions just above the plasmapause and at L ~ 3.5–5.5. Spatiotemporal variations . . .
Date: 05/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL083446 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083446
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Authors: Hartley D. P., Kletzing C A, Chen L, Horne R B, and ík O.
Title: Van Allen Probes observations of chorus wave vector orientations: Implications for the chorus-to-hiss mechanism
Abstract: Using observations from the Van Allen Probes EMFISIS instrument, coupled with ray tracing simulations, we determine the fraction of chorus wave power with the conditions required to access the plasmasphere and evolve into plasmaspheric hiss. It is found that only an extremely small fraction of chorus occurs with the required wave vector orientation, carrying only a small fraction of the total chorus wave power. The exception is on the edge of plasmaspheric plumes, where strong azimuthal density gradients are present. In these cases, up to 94% of chorus wave power exists with the conditions required to access the plasmasphere. As such, we conclude that strong azimuthal density gradients are actually a requirement if a significant fraction of chorus wave power is to enter the plasmasphere an. . .
Date: 02/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082111 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082111
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2018
Authors: Boardsen Scott A., Hospodarsky George B., Min Kyungguk, Averkamp Terrance F., Bounds Scott R., et al.
Title: Determining the wave vector direction of equatorial fast magnetosonic waves
Abstract: We perform polarization analysis of the equatorial fast magnetosonic waves electric field over a 20 minute interval of Van Allen Probes A Waveform Receiver burst mode data. The wave power peaks at harmonics of the proton cyclotron frequency indicating the spacecraft is near or in the source region. The wave vector is inferred from the direction of the major axis of the electric field polarization ellipsoid and the sign of the phase between the longitudinal electric and compressional magnetic field components. We show that wave vector is preferentially in the azimuthal direction as opposed to the radial direction. From Poynting flux analysis one would infer that the wave vector is primarily in the radial direction. We show that the error in the Poynting flux is large ~ 90°. These results s. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078695 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078695
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Authors: Hartinger M. D., Claudepierre S G, Turner D. L., Reeves G D, Breneman A., et al.
Title: Diagnosis of ULF Wave-Particle Interactions With Megaelectron Volt Electrons: The Importance of Ultrahigh-Resolution Energy Channels
Abstract: Electron flux measurements are an important diagnostic for interactions between ultralow‐frequency (ULF) waves and relativistic (∼1 MeV) electrons. Since measurements are collected by particle detectors with finite energy channel width, they are affected by a phase mixing process that can obscure these interactions. We demonstrate that ultrahigh‐resolution electron measurements from the Magnetic Electron Ion Spectrometer on the Van Allen Probes mission—obtained using a data product that improves the energy resolution by roughly an order of magnitude—are crucial for understanding ULF wave‐particle interactions. In particular, the ultrahigh‐resolution measurements reveal a range of complex dynamics that cannot be resolved by standard measurements. Furthermore, the standard meas. . .
Date: 10/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080291 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080291
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Authors: Liu Bin, Li Liuyuan, Yu Jiang, and Cao Jinbin
Title: The Effect of Hot Protons on Magnetosonic Waves Inside and Outside the Plasmapause: New Observations and Theoretic Results
Abstract: Based on the wave and proton observations by Van Allen Probes A and B, we examined the effects of hot protons (0.01–50 keV) on fast magnetosonic (MS) waves inside and outside the Earth's plasmasphere. In the low-density plasma trough outside the plasmapause, the gyroresonance interactions between hot protons and MS waves not only cause the MS wave growth at some frequencies but also lead to the damping of MS waves at other frequencies, which depends on the proton phase space density gradient and the ambient plasma density. The gyroresonance of the observed hot protons cannot excite MS waves near the lower hybrid resonance frequency and even causes the MS wave damping. Thus, the frequencies of the observed MS waves outside the plasmapause are usually lower than the lower hybrid resonance . . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024676 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024676/full
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Authors: Mager Pavel N., Mikhailova Olga S., Mager Olga V., and Klimushkin Dmitri Yu.
Title: Eigenmodes of the transverse Alfvénic resonator at the plasmapause: a Van Allen Probes case study
Abstract: A Pc4 ULF wave was detected at spacecraft B of the Van Allen Probes at the plasmapause. A distinctive feature of this wave is the strong periodical modulation of the wave. It is assumed that this modulation is a beating of oscillations close in frequency: at least two harmonics with frequencies of 15.3 and 13.6 MHz are found. It is shown that these harmonics can be the eigenmodes of the transverse resonator at the local maximum of the Alfvén velocity. In addition, the observed wave was in a drift resonance with energetic 80 keV protons and could be generated by an unstable “bump on tail” distribution of protons simultaneously observed with the wave. The estimate of the azimuthal wave number m made from the drift resonance condition gives a value of about −100, i.e., it is a westward. . .
Date: 09/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079596 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079596
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Authors: Min Kyungguk, Liu Kaijun, Wang Xueyi, Chen Lunjin, and Denton Richard E
Title: Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism
Abstract: Linear Vlasov theory and particle-in-cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Ωp and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, ∂fp/∂v⊥>0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to hav. . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024867 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024867/full
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Authors: He Yihua, Xiao Fuliang, Su Zhenpeng, Zheng Huinan, Yang Chang, et al.
Title: Generation of lower L -shell dayside chorus by energetic electrons from the plasmasheet
Abstract: Currently, the generation mechanism for the lower L‐shell dayside chorus has still remained an open question. Here, we report two storm events: 06‐07 March 2016 and 20‐21 January 2016, when Van Allen Probes observed enhanced dayside chorus with lower and higher wave normal angles (the angles between the wave vector and the geomagnetic field) in the region of L = 3.5‐6.3 and MLT = 5.6‐13.5. Hot and energetic (∼ 1‐100 keV) electrons displayed enhancements in fluxes and anisotropy when they were injected from the plasmasheet and drifted from midnight through dawn toward the dayside. Calculations of chorus local growth rates under different waves normal angles show that the upper cutoff and peak wave frequencies display similar patterns to the observations. Chorus growth rates ma. . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2017JA024889 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JA024889
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Authors: áhlava J., ěmec F., ík O., šová I., Hospodarskyy G. B., et al.
Title: Longitudinal dependence of whistler mode electromagnetic waves in the Earth's inner magnetosphere
Abstract: We use the measurements performed by the DEMETER (2004‐2010) and the Van Allen Probes (2012‐2016, still operating) spacecraft to investigate the longitudinal dependence of the intensity of whistler mode waves in the Earth's inner magnetosphere. We show that a significant longitudinal dependence is observed inside the plasmasphere on the nightside, primarily in the frequency range 400 Hz–2 kHz. On the other hand, almost no longitudinal dependence is observed on the dayside. The obtained results are compared to the lightning occurrence rate provided by the OTD/LIS mission normalized by a factor accounting for the ionospheric attenuation. The agreement between the two dependencies indicates that lightning generated electromagnetic waves may be responsible for the observed effect, thus s. . .
Date: 07/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025284 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025284
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Authors: Liu Nigang, Su Zhenpeng, Zheng Huinan, Wang Yuming, and Wang Shui
Title: Magnetosonic harmonic falling and rising frequency emissions potentially generated by nonlinear wave-wave interactions in the Van Allen radiation belts
Abstract: Magnetosonic waves play a potentially important role in the complex evolution of the radiation belt electrons. These waves typically appear as discrete emission lines along the proton gyrofrequency harmonics, consistent with the prediction of the local Bernstein mode instability of hot proton ring distributions. Magnetosonic waves are nearly dispersionless particularly at low harmonics and therefore have the roughly unchanged frequency‐time structures during the propagation. On the basis of Van Allen Probes observations, we here present the first report of magnetosonic harmonic falling and rising frequency emissions. They lasted for up to 2 h and occurred primarily in the dayside plasmatrough following intense substorms. These harmonic emission lines were well spaced by the proton gyrofr. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079232 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079232
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Authors: Li Li, Zhou Xu-Zhi, Omura Yoshiharu, Wang Zi-Han, Zong Qiu-Gang, et al.
Title: Nonlinear drift resonance between charged particles and ultra-low frequency waves: Theory and Observations
Abstract: In Earth's inner magnetosphere, electromagnetic waves in the ultra‐low frequency (ULF) range play an important role in accelerating and diffusing charged particles via drift resonance. In conventional drift‐resonance theory, linearization is applied under the assumption of weak wave‐particle energy exchange so particle trajectories are unperturbed. For ULF waves with larger amplitudes and/or durations, however, the conventional theory becomes inaccurate since particle trajectories are strongly perturbed. Here, we extend the drift‐resonance theory into a nonlinear regime, to formulate nonlinear trapping of particles in a wave‐carried potential well, and predict the corresponding observable signatures such as rolled‐up structures in particle energy spectrum. After considering how. . .
Date: 08/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079038 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079038
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Authors: Agapitov O., Drake J. F., Vasko I., Mozer F S, Artemyev A., et al.
Title: Nonlinear Electrostatic Steepening of Whistler Waves: The Guiding Factors and Dynamics in Inhomogeneous Systems
Abstract: Whistler mode chorus waves are particularly important in outer radiation belt dynamics due to their key role in controlling the acceleration and scattering of electrons over a very wide energy range. The efficiency of wave‐particle resonant interactions is defined by whistler wave properties which have been described by the approximation of plane linear waves propagating through the cold plasma of the inner magnetosphere. However, recent observations of extremely high‐amplitude whistlers suggest the importance of nonlinear wave‐particle interactions for the dynamics of the outer radiation belt. Oblique chorus waves observed in the inner magnetosphere often exhibit drastically nonsinusoidal (with significant power in the higher harmonics) waveforms of the parallel electric field, pres. . .
Date: 03/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL076957 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2017GL076957
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Authors: Agapitov O., Drake J. F., Vasko I., Mozer F S, Artemyev A., et al.
Title: Nonlinear Electrostatic Steepening of Whistler Waves: The Guiding Factors and Dynamics in Inhomogeneous Systems
Abstract: Whistler mode chorus waves are particularly important in outer radiation belt dynamics due to their key role in controlling the acceleration and scattering of electrons over a very wide energy range. The efficiency of wave‐particle resonant interactions is defined by whistler wave properties which have been described by the approximation of plane linear waves propagating through the cold plasma of the inner magnetosphere. However, recent observations of extremely high‐amplitude whistlers suggest the importance of nonlinear wave‐particle interactions for the dynamics of the outer radiation belt. Oblique chorus waves observed in the inner magnetosphere often exhibit drastically nonsinusoidal (with significant power in the higher harmonics) waveforms of the parallel electric field, pres. . .
Date: 03/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL076957 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2017GL076957
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Authors: Teng S., Zhao J., Tao X., Wang S., and Reeves G D
Title: Observation of Oblique Lower Band Chorus Generated by Nonlinear Three-Wave Interaction
Abstract: Oblique whistler mode waves have been suggested to play an important role in radiation belt electron dynamics. Recently, Fu et al. [2017] proposed that highly oblique lower band whistler waves could be generated by nonlinear three‐wave resonance. Here we present the first observational evidence of such process, using Van Allen Probes data, where an oblique lower band chorus wave is generated by two quasi‐parallel waves through nonlinear three‐wave interaction. The wave resonance condition is satisfied even in the presence of frequency chirping of one of the pump waves. Different from the simulation results of Fu et al. [2017], simultaneous particle data do not show a plateau in the electron distribution, which could be due to the very weak intensity of the generated waves. These resu. . .
Date: 06/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078765 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078765
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Authors: Teng S., Zhao J., Tao X., Wang S., and Reeves G D
Title: Observation of Oblique Lower Band Chorus Generated by Nonlinear Three-Wave Interaction
Abstract: Oblique whistler mode waves have been suggested to play an important role in radiation belt electron dynamics. Recently, Fu et al. [2017] proposed that highly oblique lower band whistler waves could be generated by nonlinear three‐wave resonance. Here we present the first observational evidence of such process, using Van Allen Probes data, where an oblique lower band chorus wave is generated by two quasi‐parallel waves through nonlinear three‐wave interaction. The wave resonance condition is satisfied even in the presence of frequency chirping of one of the pump waves. Different from the simulation results of Fu et al. [2017], simultaneous particle data do not show a plateau in the electron distribution, which could be due to the very weak intensity of the generated waves. These resu. . .
Date: 06/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078765 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078765
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Authors: Ripoll ‐F., Loridan V., Denton M. H., Cunningham G., Reeves G., et al.
Title: Observations and Fokker‐Planck simulations of the L‐shell, energy, and pitch‐angle structure of Earth’s electron radiation belts during quiet times
Abstract: The evolution of the radiation belts in L‐shell (L), energy (E), and equatorial pitch‐angle (α0) is analyzed during the calm 11‐day interval (March 4 –March 15) following the March 1 storm 2013. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker‐Planck simulations combined with consistent event‐driven scattering modeling from whistler mode hiss waves. Three (L, E, α0)‐regions persist through 11 days of hiss wave scattering; the pitch‐angle dependent inner belt core (L~<2.2 and E<700 keV), pitch‐angle homogeneous outer belt low‐energy core (L>~5 and E~<100 keV), and a distinct pocket of electrons (L~[4.5, 5.5] and E~[0.7, 2] MeV). The pitch‐angle homogeneous outer belt is explained by the diff. . .
Date: 12/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026111 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026111
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Authors: Yuan Zhigang, Liu Kun, Yu Xiongdong, Yao Fei, Huang Shiyong, et al.
Title: Precipitation of radiation belt electrons by EMIC waves with conjugated observations of NOAA and Van Allen satellites
Abstract: In this letter, we present unique conjugated satellite observations of MeV relativistic electron precipitation caused by electromagnetic ion cyclotron (EMIC) waves. On the outer boundary of the plasmasphere, the Van Allen probe observed EMIC waves. At ionospheric altitudes, the NOAA 16 satellite at the footprint of Van Allen probe simultaneously detected obvious flux enhancements for precipitating >MeV radiation belt electrons, but not for precipitating MeV radiation belt electrons. Our result provides a direct magnetic conjugated observational link between in‐situ inner magnetospheric EMIC wav. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080481 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080481
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Authors: Liu Nigang, Su Zhenpeng, Zheng Huinan, Wang Yuming, and Wang Shui
Title: Prompt Disappearance and Emergence of Radiation Belt Magnetosonic Waves Induced by Solar Wind Dynamic Pressure Variations
Abstract: Magnetosonic waves are highly oblique whistler mode emissions transferring energy from the ring current protons to the radiation belt electrons in the inner magnetosphere. Here we present the first report of prompt disappearance and emergence of magnetosonic waves induced by the solar wind dynamic pressure variations. The solar wind dynamic pressure reduction caused the magnetosphere expansion, adiabatically decelerated the ring current protons for the Bernstein mode instability, and produced the prompt disappearance of magnetosonic waves. On the contrary, because of the adiabatic acceleration of the ring current protons by the solar wind dynamic pressure enhancement, magnetosonic waves emerged suddenly. In the absence of impulsive injections of hot protons, magnetosonic waves were observa. . .
Date: 01/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL076382 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL076382/full
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Authors: Zhang X.-J., Thorne R., Artemyev A., Mourenas D., Angelopoulos V, et al.
Title: Properties of intense field-aligned lower-band chorus waves: Implications for nonlinear wave-particle interactions
Abstract: Resonant interactions between electrons and chorus waves are responsible for a wide range of phenomena in near‐Earth space (e.g., diffuse aurora, acceleration of MeV electrons, etc.). Although quasi‐linear diffusion is believed to be the primary paradigm for describing such interactions, an increasing number of investigations suggest that nonlinear effects are also important in controlling the rapid dynamics of electrons. However, present models of nonlinear wave‐particle interactions, which have been successfully used to describe individual short‐term events, are not directly applicable for a statistical evaluation of nonlinear effects and the long‐term dynamics of the outer radiation belt, because they lack information on the properties of intense (nonlinearly resonating with e. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025390 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025390
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Authors: Hartley D. P., Kletzing C A, ík O., Chen L, and Horne R B
Title: Statistical Properties of Plasmaspheric Hiss from Van Allen Probes Observations
Abstract: Van Allen Probes observations are used to statistically investigate plasmaspheric hiss wave properties. This analysis shows that the wave normal direction of plasmaspheric hiss is predominantly field aligned at larger L shells, with a bimodal distribution, consisting of a near-field aligned and a highly oblique component, becoming apparent at lower L shells. Investigation of this oblique population reveals that it is most prevalent at L < 3, frequencies with f/fce> 0.01 (or f> 700 Hz), low geomagnetic activity levels, and between 1900 and 0900 MLT. This structure is similar to that reported for oblique chorus waves in the equatorial region, perhaps suggesting a causal link between the two wave modes. Ray tracing results from HOTRAY confirm that is feasible for these oblique chorus waves to. . .
Date: 02/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024593 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024593/full
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Authors: Xiang Zheng, Tu Weichao, Ni Binbin, Henderson M G, and Cao Xing
Title: A Statistical Survey of Radiation Belt Dropouts Observed by Van Allen Probes
Abstract: A statistical analysis on the radiation belt dropouts is performed based on 4 years of electron phase space density data from the Van Allen Probes. The μ, K, and L* dependence of dropouts and their driving mechanisms and geomagnetic and solar wind conditions are investigated using electron phase space density data sets for the first time. Our results suggest that electronmagnetic ion cyclotron (EMIC) wave scattering is the dominant dropout mechanism at low L* region, which requires the most active geomagnetic and solar wind conditions. In contrast, dropouts at high L* have a higher occurrence and are due to a combination of EMIC wave scattering and outward radial diffusion associated with magnetopause shadowing. In addition, outward radial diffusion at high L* is found to cause larger dro. . .
Date: 08/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078907 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078907
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Authors: Yang Chang, Xiao Fuliang, He Yihua, Liu Si, Zhou Qinghua, et al.
Title: Storm-time evolution of outer radiation belt relativistic electrons by a nearly continuous distribution of chorus
Abstract: During the 13-14 November 2012 storm, Van Allen Probe A simultaneously observed a 10-h period of enhanced chorus (including quasi-parallel and oblique propagation components) and relativistic electron fluxes over a broad range of L = 3−6 and MLT=2 − 10 within a complete orbit cycle. By adopting a Gaussian fit to the observed wave spectra, we obtain the wave parameters and calculate the bounce-averaged diffusion coefficients. We solve the Fokker-Planck diffusion equation to simulate flux evolutions of relativistic (1.8-4.2 MeV) electrons during two intervals when Probe A passed the location L = 4.3 along its orbit. The simulating results show that chorus with combined quasi-parallel and oblique components can produce a more pronounced flux enhancement in the pitch angle range ∼45∘. . .
Date: 02/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL075894 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL075894/full
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Authors: Yang Chang, Xiao Fuliang, He Yihua, Liu Si, Zhou Qinghua, et al.
Title: Storm-time evolution of outer radiation belt relativistic electrons by a nearly continuous distribution of chorus
Abstract: During the 13-14 November 2012 storm, Van Allen Probe A simultaneously observed a 10-h period of enhanced chorus (including quasi-parallel and oblique propagation components) and relativistic electron fluxes over a broad range of L = 3−6 and MLT=2 − 10 within a complete orbit cycle. By adopting a Gaussian fit to the observed wave spectra, we obtain the wave parameters and calculate the bounce-averaged diffusion coefficients. We solve the Fokker-Planck diffusion equation to simulate flux evolutions of relativistic (1.8-4.2 MeV) electrons during two intervals when Probe A passed the location L = 4.3 along its orbit. The simulating results show that chorus with combined quasi-parallel and oblique components can produce a more pronounced flux enhancement in the pitch angle range ∼45∘. . .
Date: 02/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL075894 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL075894/full
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Authors: Capannolo L., Li W, Ma Q, Zhang X.-J., Redmon R. J., et al.
Title: Understanding the Driver of Energetic Electron Precipitation Using Coordinated Multisatellite Measurements
Abstract: Magnetospheric plasma waves play a significant role in ring current and radiation belt dynamics, leading to pitch angle scattering loss and/or stochastic acceleration of the particles. During a non‐storm time dropout event on 24 September 2013, intense electromagnetic ion cyclotron (EMIC) waves were detected by Van Allen Probe A (Radiation Belt Storm Probes‐A). We quantitatively analyze a conjunction event when Van Allen Probe A was located approximately along the same magnetic field line as MetOp‐01, which detected simultaneous precipitation of >30 keV protons and energetic electrons over an unexpectedly broad energy range (>~30 keV). Multipoint observations together with quasi‐linear theory provide direct evidence that the observed electron precipitation at higher energy (>~700 k. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078604 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078604
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Authors: Malaspina David M., Ripoll Jean-Francois, Chu Xiangning, Hospodarsky George, and Wygant John
Title: Variation in Plasmaspheric Hiss Wave Power With Plasma Density
Abstract: Plasmaspheric hiss waves are commonly observed in the inner magnetosphere. These waves efficiently scatter electrons, facilitating their precipitation into the atmosphere. Predictive inner magnetosphere simulations often model hiss waves using parameterized empirical maps of observed hiss power. These maps nearly always include parameterization by magnetic L value. In this work, data from the Van Allen Probes are used to compare variation in hiss wave power with variation in both L value and cold plasma density. It is found that for L> 2.5, plasmaspheric hiss wave power increases with plasma density. For L> 3, this increase is stronger and occurs regardless of L value and for all local times. This result suggests that the current paradigm for parameterizing hiss wave power in many magnetos. . .
Date: 09/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078564 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078564
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2017
Authors: Crabtree Chris, Ganguli Gurudas, and Tejero Erik
Title: Analysis of self-consistent nonlinear wave-particle interactions of whistler waves in laboratory and space plasmas
Abstract: Whistler mode chorus is one of the most important emissions affecting the energization of the radiation belts. Recent laboratory experiments that inject energetic electron beams into a cold plasma have revealed several spectral features in the nonlinear evolution of these instabilities that have also been observed in high-time resolution in situ wave-form data. These features include (1) a sub-element structure which consists of an amplitude modulation on time-scales slower than the bounce time, (2) closely spaced discrete frequency hopping that results in a faster apparent frequency chirp rate, (3) fast frequency changes near the sub-element boundaries, and (4) harmonic generation. In this paper, we develop a finite dimensional self-consistent Hamiltonian model for the evolution of the re. . .
Date: 03/2017 Publisher: Physics of Plasmas Pages: 056501 DOI: 10.1063/1.4977539 Available at: http://aip.scitation.org/doi/10.1063/1.4977539
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Authors: Crabtree Chris, Tejero Erik, Ganguli Gurudas, Hospodarsky George B., and Kletzing Craig A.
Title: Bayesian Spectral Analysis of Chorus Sub-Elements from the Van Allen Probes
Abstract: We develop a Bayesian spectral analysis technique that calculates the probability distribution functions of a superposition of wave-modes each described by a linear growth rate, a frequency and a chirp rate. The Bayesian framework has a number of advantages, including 1) reducing the parameter space by integrating over the amplitude and phase of the wave, 2) incorporating the data from each channel to determine the model parameters such as frequency which leads to high resolution results in frequency and time, 3) the ability to consider the superposition of waves where the wave-parameters are closely spaced, 4) the ability to directly calculate the expectation value of wave parameters without resorting to ensemble averages, 5) the ability to calculate error bars on model parameters. We exa. . .
Date: 04/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023547 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023547/full
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Authors: Cao Xing, Ni Binbin, Summers Danny, Zou Zhengyang, Fu Song, et al.
Title: Bounce resonance scattering of radiation belt electrons by low-frequency hiss: Comparison with cyclotron and Landau resonances
Abstract: Bounce-resonant interactions with magnetospheric waves have been proposed as important contributing mechanisms for scattering near-equatorially mirroring electrons by violating the second adiabatic invariant associated with the electron bounce motion along a geomagnetic field line. This study demonstrates that low-frequency plasmaspheric hiss with significant wave power below 100 Hz can bounce-resonate efficiently with radiation belt electrons. By performing quantitative calculations of pitch-angle scattering rates, we show that low-frequency hiss induced bounce-resonant scattering of electrons has a strong dependence on equatorial pitch-angle αeq. For electrons with αeq close to 90°, the timescale associated with bounce resonance scattering can be comparable to or even less than 1 hour. . .
Date: 09/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL075104 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL075104/full
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Authors: Yue Chao, Bortnik Jacob, Thorne Richard M, Ma Qianli, An Xin, et al.
Title: The characteristic pitch angle distributions of 1 eV to 600 keV protons near the equator based on Van Allen Probes observations
Abstract: Understanding the source and loss processes of various plasma populations is greatly aided by having accurate knowledge of their pitch angle distributions (PADs). Here, we statistically analyze ~1 eV to 600 keV hydrogen (H+) PADs near the geomagnetic equator in the inner magnetosphere based on Van Allen Probes measurements, to comprehensively investigate how the H+ PADs vary with different energies, magnetic local times (MLTs), L-shells, and geomagnetic conditions. Our survey clearly indicates four distinct populations with different PADs: (1) a pancake distribution of the plasmaspheric H+ at low L-shells except for dawn sector; (2) a bi-directional field-aligned distribution of the warm plasma cloak; (3) pancake or isotropic distributions of ring current H+; (4) radiation belt particles s. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024421 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024421/full
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Authors: Yue Chao, Chen Lunjin, Bortnik Jacob, Ma Qianli, Thorne Richard M, et al.
Title: The characteristic response of whistler mode waves to interplanetary shocks
Abstract: Magnetospheric whistler mode waves play a key role in regulating the dynamics of the electron radiation belts. Recent satellite observations indicate a significant influence of interplanetary (IP) shocks on whistler mode wave power in the inner magnetosphere. In this study, we statistically investigate the response of whistler mode chorus and plasmaspheric hiss to IP shocks based on Van Allen Probes and THEMIS satellite observations. Immediately after the IP shock arrival, chorus wave power is usually intensified, often at post-midnight to pre-noon sector, while plasmaspheric hiss wave power predominantly decreases near the dayside but intensifies near the nightside. We conclude that chorus wave intensification outside the plasmasphere is probably associated with the suprathermal electron . . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024574 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024574/full
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Authors: Li Jinxing, Bortnik Jacob, An Xin, Li Wen, Thorne Richard M, et al.
Title: Chorus Wave Modulation of Langmuir Waves in the Radiation Belts
Abstract: Using high-resolution waveforms measured by the Van Allen Probes, we report a novel observation in the radiation belts. Namely, we show that multiband, discrete, rising-tone whistler mode chorus emissions exhibit a one-to-one correlation with Langmuir wave bursts. Moreover, the periodic Langmuir wave bursts are generally observed at the phase location where the chorus wave E|| component is oriented opposite to its propagation direction. The electron measurements show a beam in phase space density at the particle velocity that matches the parallel phase velocity of the chorus waves. Based on this evidence, we conclude that the chorus waves accelerate the suprathermal electrons via Landau resonance and generate a localized electron beam in phase space density. Consequently, the Langmuir wave. . .
Date: 12/2017 Publisher: Geophysical Research Letters Pages: 11,713 - 11,721 DOI: 10.1002/2017GL075877 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL075877/full
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Authors: Aryan Homayon, Sibeck David G., Bin Kang Suk-, Balikhin Michael A., Fok Mei-Ching, et al.
Title: CIMI simulations with newly developed multi-parameter chorus and plasmaspheric hiss wave models
Abstract: Numerical simulation studies of the Earth's radiation belts are important to understand the acceleration and loss of energetic electrons. The Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model considers the effects of the ring current and plasmasphere on the radiation belts to obtain plausible results. The CIMI model incorporates pitch angle, energy, and cross diffusion of electrons, due to chorus and plasmaspheric hiss waves. These parameters are calculated using statistical wave distribution models of chorus and plasmaspheric hiss amplitudes. However, currently these wave distribution models are based only on a single parameter, geomagnetic index (AE), and could potentially underestimate the wave amplitudes. Here we incorporate recently developed multi-parameter chorus and plasmas. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024159 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024351/full
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Authors: Li Jinxing, Bortnik Jacob, Li Wen, Thorne Richard M., Ma Qianli, et al.
Title: Coherently modulated whistler mode waves simultaneously observed over unexpectedly large spatial scales
Abstract: Utilizing simultaneous twin Van Allen Probes observations of whistler mode waves at variable separations, we are able to distinguish the temporal variations from spatial variations, determine the coherence spatial scale, and suggest the possible mechanism of wave modulation. The two probes observed coherently modulated whistler mode waves simultaneously at an unexpectedly large distance up to ~4.3 RE over 3 h during a relatively quiet period. The modulation of 150–500 Hz plasmaspheric hiss was correlated with whistler mode waves measured outside the plasmasphere across 3 h in magnetic local time and 3 L shells, revealing that the modulation was temporal in nature. We suggest that the coherent modulation of whistler mode waves was associated with the coherent ULF waves measured ov. . .
Date: 02/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023706 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023706/full
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Authors: Li Jinxing, Bortnik Jacob, Li Wen, Thorne Richard M, Ma Qianli, et al.
Title: Coherently modulated whistler mode waves simultaneously observed over unexpectedly large spatial scales
Abstract: Utilizing simultaneous twin Van Allen Probes observations of whistler mode waves at variable separations, we are able to distinguish the temporal variations from spatial variations, determine the coherence spatial scale, and suggest the possible mechanism of wave modulation. The two probes observed coherently modulated whistler mode waves simultaneously at an unexpectedly large distance up to ~4.3 RE over 3 h during a relatively quiet period. The modulation of 150–500 Hz plasmaspheric hiss was correlated with whistler mode waves measured outside the plasmasphere across 3 h in magnetic local time and 3 L shells, revealing that the modulation was temporal in nature. We suggest that the coherent modulation of whistler mode waves was associated with the coherent ULF waves measured ov. . .
Date: 02/2017 Publisher: Journal of Geophysical Research: Space Physics Pages: 1871-1882 DOI: 10.1002/2016JA023706 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023706/full
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Authors: Zhang X.-J., Mourenas D., Artemyev A. V., Angelopoulos V, and Thorne R M
Title: Contemporaneous EMIC and Whistler-Mode Waves: Observations and Consequences for MeV Electron Loss
Abstract: The high variability of relativistic (MeV) electron fluxes in the Earth's radiation belts is partly controlled by loss processes involving resonant interactions with electromagnetic ion cyclotron (EMIC) and whistler-mode waves. But as previous statistical models were generated independently for each wave mode, whether simultaneous electron scattering by the two wave types has global importance remains an open question. Using >3 years of simultaneous Van Allen Probes and THEMIS measurements, we explore the contemporaneous presence of EMIC and whistler-mode waves in the same L-shell, albeit at different local times, determining the distribution of wave and plasma parameters as a function of L, Kp, and AE. We derive electron lifetimes from observations and provide the first statistics of comb. . .
Date: 07/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073886 Available at: onlinelibrary.wiley.com/doi/10.1002/2017GL073886/full
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