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2017
Authors: Moya Pablo. S., Pinto íctor A., Sibeck David G., Kanekal Shrikanth G, and Baker Daniel N
Title: On the effect of geomagnetic storms on relativistic electrons in the outer radiation belt: Van Allen Probes observations
Abstract: Using Van Allen Probes ECT-REPT observations we performed a statistical study on the effect of geomagnetic storms on relativistic electrons fluxes in the outer radiation belt for 78 storms between September 2012 and June 2016. We found that the probability of enhancement, depletion and no change in flux values depends strongly on L and energy. Enhancement events are more common for ∼ 2 MeV electrons at L ∼ 5, and the number of enhancement events decreases with increasing energy at any given L shell. However, considering the percentage of occurrence of each kind of event, enhancements are more probable at higher energies, and the probability of enhancement tends to increases with increasing L shell. Depletion are more probable for 4-5 MeV electrons at the heart of the outer radiation be. . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024735 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024735/full
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Authors: Zhelavskaya Irina S., Shprits Yuri Y, and ć Maria
Title: Empirical modeling of the plasmasphere dynamics using neural networks
Abstract: We propose a new empirical model for reconstructing the global dynamics of the cold plasma density distribution based only on solar wind data and geomagnetic indices. Utilizing the density database obtained using the NURD (Neural-network-based Upper hybrid Resonance Determination) algorithm for the period of October 1, 2012 - July 1, 2016, in conjunction with solar wind data and geomagnetic indices, we develop a neural network model that is capable of globally reconstructing the dynamics of the cold plasma density distribution for 2≤L≤6 and all local times. We validate and test the model by measuring its performance on independent datasets withheld from the training set and by comparing the model predicted global evolution with global images of He+ distribution in the Earth's plasmasph. . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024406 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024406/full
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Authors: Denton M. H., Thomsen M F, Reeves G D, Larsen B A, Henderson M G, et al.
Title: The Evolution of the Plasma Sheet Ion Composition: Storms and Recoveries
Abstract: The ion plasma sheet (~few hundred eV to ~few 10s keV) is usually dominated by H+ ions. Here, changes in ion composition within the plasma sheet are explored both during individual events, and statistically during 54 calm-to-storm events and during 21 active-to-calm events. Ion composition data from the HOPE (Helium, Oxygen, Proton, Electron) instruments onboard Van Allen Probes satellites provide exceptional spatial and temporal resolution of the H+, O+, and He+ ion fluxes in the plasma sheet. H+ shown to be the dominant ion in the plasma sheet in the calm-to-storm transition. However, the energy-flux of each ion changes in a quasi-linear manner during extended calm intervals. Heavy ions (O+ and He+) become increasingly important during such periods as charge-exchange reactions result in . . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024475 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024475/full
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Authors: Turner D. L., Lee J. H., Claudepierre S G, Fennell J. F., Blake J B, et al.
Title: Examining coherency scales, substructure, and propagation of whistler-mode chorus elements with Magnetospheric Multiscale (MMS)
Abstract: Whistler-mode chorus waves are a naturally occurring electromagnetic emission observed in Earth's magnetosphere. Here, for the first time, data from NASA's Magnetospheric Multiscale (MMS) mission were used to analyze chorus waves in detail, including the calculation of chorus wave normal vectors, k. A case study was examined from a period of substorm activity around the time of a conjunction between the MMS constellation and NASA's Van Allen Probes mission on 07 April 2016. Chorus wave activity was simultaneously observed by all six spacecraft over a broad range of L-shells (5.5 < L < 8.5), magnetic local time (06:00 < MLT < 09:00), and magnetic latitude (-32° < MLat < -15°), implying a large chorus active region. Eight chorus elements and their substructure were analyzed in detail with . . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024474 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024474/full
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Authors: Brito Thiago V., and Morley Steven K.
Title: Improving empirical magnetic field models by fitting to in situ data using an optimized parameter approach
Abstract: A method for comparing and optimizing the accuracy of empirical magnetic field models using in situ magnetic field measurements is presented. The optimization method minimizes a cost function - τ - that explicitly includes both a magnitude and an angular term. A time span of 21 days, including periods of mild and intense geomagnetic activity, was used for this analysis. A comparison between five magnetic field models (T96, T01S, T02, TS04, TS07) widely used by the community demonstrated that the T02 model was, on average, the most accurate when driven by the standard model input parameters. The optimization procedure, performed in all models except TS07, generally improved the results when compared to unoptimized versions of the models. Additionally, using more satellites in the optimizat. . .
Date: 10/2017 Publisher: Space Weather DOI: 10.1002/2017SW001702 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017SW001702/full
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Authors: McCollough J. P., Quinn J. M., Starks M. J., and Johnston W R
Title: Intelligent Sampling of Hazardous Particle Populations in Resource-Constrained Environments
Abstract: Sampling of anomaly-causing space environment drivers is necessary for both real-time operations and satellite design efforts, and optimizing measurement sampling helps minimize resource demands. Relating these measurements to spacecraft anomalies requires the ability to resolve spatial and temporal variability in the energetic charged particle hazard of interest. Here we describe a method for sampling particle fluxes informed by magnetospheric phenomenology so that, along a given trajectory, the variations from both temporal dynamics and spatial structure are adequately captured while minimizing oversampling. We describe the coordinates, sampling method, and specific regions and parameters employed. We compare resulting sampling cadences with data from spacecraft spanning the regions of i. . .
Date: 10/2017 Publisher: Space Weather DOI: 10.1002/2017SW001629 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017SW001629/full
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Authors: Matsui H., Torbert R B, Spence H E, Argall M. R., Alm L., et al.
Title: Relativistic electron increase during chorus wave activities on the 6-8 March 2016 geomagnetic storm
Abstract: There was a geomagnetic storm on 6–8 March 2016, in which Van Allen Probes A and B separated by ∼2.5 h measured increase of relativistic electrons with energies ∼ several hundred keV to 1 MeV. Simultaneously, chorus waves were measured by both Van Allen Probes and Magnetospheric Multiscale (MMS) mission. Some of the chorus elements were rising-tones, possibly due to nonlinear effects. These measurements are compared with a nonlinear theory of chorus waves incorporating the inhomogeneity ratio and the field equation. From this theory, a chorus wave profile in time and one-dimensional space is simulated. Test particle calculations are then performed in order to examine the energization rate of electrons. Some electrons are accelerated, although more electrons are decelerated. The measu. . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024540 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024540/full
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Authors: Kim S.-I., Kim K.-H., Kwon H.-J., Jin H., Lee E., et al.
Title: SC-associated electric field variations in the magnetosphere and ionospheric convective flows
Abstract: We examine magnetic and electric field perturbations associated with a sudden commencement (SC), caused by an interplanetary (IP) shock passing over the Earth's magnetosphere on 16 February 2013. The SC was identified in the magnetic and electric field data measured at THEMIS-E (THE-E: MLT = 12.4, L = 6.3), Van Allen Probe-A (VAP-A: MLT = 3.2, L = 5.1), and Van Allen Probe-B (VAP-B: MLT = 0.2. L= 4.9) in the magnetosphere. During the SC interval, THE-E observed a dawnward-then-duskward electric (E) field perturbation around noon, while VAP-B observed a duskward E-field perturbation around midnight. VAP-A observed a dawnward-then-duskward E-field perturbation in the postmidnight sector, but the duration and magnitude of the dawnward E-perturbation are much shorter and weaker than that at TH. . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024611 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024611/full
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Authors: Liu Nigang, Su Zhenpeng, Gao Zhonglei, Reeves G D, Zheng Huinan, et al.
Title: Shock-induced disappearance and subsequent recovery of plasmaspheric hiss: Coordinated observations of RBSP, THEMIS and POES satellites
Abstract: Plasmaspheric hiss is an extremely low frequency whistler-mode emission contributing significantly to the loss of radiation belt electrons. There are two main competing mechanisms for the generation of plasmaspheric hiss: excitation by local instability in the outer plasmasphere and origination from chorus outside the plasmasphere. Here, on the basis of the analysis of an event of shock-induced disappearance and subsequent recovery of plasmaspheric hiss observed by RBSP, THEMIS and POES missions, we attempt to identify its dominant generation mechanism. In the pre-shock plasmasphere, the local electron instability was relatively weak and the hiss waves with bidirectional Poynting fluxes mainly originated from the dayside chorus waves. On arrival of the shock, the removal of pre-existing da. . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024470 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024470/full
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Authors: Shekhar Sapna, Millan Robyn, and Smith David
Title: A Statistical Study of the Spatial Extent of Relativistic Electron Precipitation with Polar Orbiting Environmental Satellites.
Abstract: Relativistic Electron Precipitation (REP) in the atmosphere can contribute significantly to electron loss from the outer radiation belts. In order to estimate the contribution to this loss, it is important to estimate the spatial extent of the precipitation region. We observed REP with the zenith pointing (0o) Medium Energy Proton Electron Detector (MEPED) on board Polar Orbiting Environmental Satellites (POES), for 15 years (2000-2014) and used both single and multi satellite measurements to estimate an average extent of the region of precipitation in L shell and Magnetic Local Time (MLT). In the duration of 15 years (2000-2014), 31035 REP events were found in this study. Events were found to split into two classes; one class of events coincided with proton precipitation in the P1 channel. . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024716 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024716/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: Jin YuYue, Yang Chang, He Yihua, Liu Si, Zhou Qinghua, et al.
Title: Butterfly distribution of Earth’s radiation belt relativistic electrons induced by dayside chorus
Abstract: Previous theoretical studies have shown that dayside chorus can produce butterfly distribution of energetic electrons in the Earth’s radiation belts by preferentially accelerating medium pitch angle electrons, but this requires the further confirmation from high-resolution satellite observation. Here, we report correlated Van Allen Probes data on wave and particle during the 11–13 April, 2014 geomagnetic storm. We find that a butterfly pitch angle distribution of relativistic electrons is formed around the location L = 4.52, corresponding to the presence of enhanced dayside chorus. Using a Gaussian distribution fit to the observed chorus spectra, we calculate the bounce-averaged diffusion rates and solve two-dimensional Fokker-Planck equation. Numerical results demonstrate that acceler. . .
Date: 09/2017 Publisher: Science China Technological Sciences DOI: 10.1007/s11431-017-9067-y Available at: https://link.springer.com/article/10.1007/s11431-017-9067-y
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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: Ma Q, Li W, Thorne R M, Bortnik J, Reeves G D, et al.
Title: Diffusive transport of several hundred keV electrons in the Earth's slot region
Abstract: We investigate the gradual diffusion of energetic electrons from the inner edge of the outer radiation belt into the slot region. The Van Allen Probes observed slow inward diffusion and decay of ~200-600 keV electrons following the intense geomagnetic storm that occurred on 17 March 2013. During the 10-day non-disturbed period following the storm, the peak of electron fluxes gradually moved from L~2.7 to L~2.4, and the flux levels decreased by a factor of ~2-4 depending on the electron energy. We simulated the radial intrusion and decay of electrons using a 3-dimentional diffusion code, which reproduced the energy-dependent transport of electrons from ~100 keV to 1 MeV in the slot region. At energies of 100-200 keV, the electrons experience fast transport across the slot region due to the . . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024452 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024452/full
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Authors: Summers Danny, Shi Run, Engebretson Mark J, Oksavik Kjellmar, Manweiler Jerry W., et al.
Title: Energetic proton spectra measured by the Van Allen Probes
Abstract: We test the hypothesis that pitch-angle scattering by electromagnetic ion cyclotron (EMIC) waves can limit ring current proton fluxes. For two chosen magnetic storms, during March 17-20, 2013 and March 17-20, 2015, we measure proton energy spectra in the region 3 ≤ L ≤ 6 using the RBSPICE B instrument on the Van Allen Probes. The most intense proton spectra are observed to occur during the recovery periods of the respective storms. Using proton precipitation data from the POES (NOAA and MetOp) spacecraft, we deduce that EMIC wave action was prevalent at the times and L-shell locations of the most intense proton spectra. We calculate limiting ring current proton energy spectra from recently developed theory. Comparisons between the observed proton energy spectra and the theoreti. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024484 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024484/full
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Authors: Fu Xiangrong, Gary Peter, Reeves Geoffrey D, Winske Dan, and Woodroffe Jesse R.
Title: Generation of Highly Oblique Lower-band Chorus via Nonlinear Three-wave Resonance
Abstract: Chorus in the inner magnetosphere has been observed frequently at geomagnetically active times, typically exhibiting a two-band structure with a quasi-parallel lower-band and an upper-band with a broad range of wave normal angles. But recent observations by Van Allen Probes confirm another type of lower-band chorus, which has a large wave normal angle close to the resonance cone angle. It has been proposed that these waves could be generated by a low-energy beam-like electron component or by temperature anisotropy of keV electrons in the presence of a low-energy plateau-like electron component. This paper, however, presents an alternative mechanism for generation of this highly oblique lower-band chorus. Through a nonlinear three-wave resonance, a quasi-parallel lower-band chorus wave can . . .
Date: 09/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074411 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL074411/full
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Authors: He Zhaoguo, Chen Lunjin, Zhu Hui, Xia Zhiyang, Reeves G D, et al.
Title: Multiple-satellite observation of magnetic dip event during the substorm on 10 October, 2013
Abstract: We present a multiple-satellite observation of the magnetic dip event during the substorm on October 10, 2013. The observation illustrates the temporal and spatial evolution of the magnetic dip and gives a compelling evidence that ring current ions induce the magnetic dip by enhanced plasma beta. The dip moves with the energetic ions in a comparable drift velocity and affects the dynamics of relativistic electrons in the radiation belt. In addition, the magnetic dip provides a favorable condition for the EMIC wave generation based on the linear theory analysis. The calculated proton diffusion coefficients show that the observed EMIC wave can lead to the pitch angle scattering losses of the ring current ions, which in turn partially relax the magnetic dip in the observations. This study enr. . .
Date: 09/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074869 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL074869/full
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Authors: Turner D. L., Fennell J. F., Blake J B, Claudepierre S G, Clemmons J. H., et al.
Title: Multipoint observations of energetic particle injections and substorm activity during a conjunction between Magnetospheric Multiscale (MMS) and Van Allen Probes
Abstract: This study examines multipoint observations during a conjunction between MMS and Van Allen Probes on 07 April 2016 in which a series of energetic particle injections occurred. With complementary data from THEMIS, Geotail, and LANL-GEO (16 spacecraft in total), we develop new insights on the nature of energetic particle injections associated with substorm activity. Despite this case involving only weak substorm activity (max. AE < 300 nT) during quiet geomagnetic conditions in steady, below-average solar wind, a complex series of at least six different electron injections was observed throughout the system. Intriguingly, only one corresponding ion injection was clearly observed. All ion and electron injections were observed at < 600 keV only. MMS reveals detailed substructure within the lar. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024554 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024554/full
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Authors: Kim Hyomin, Gerrard Andrew J., Lanzerotti Louis J., Soto-Chavez Rualdo, Cohen Ross J., et al.
Title: Ring Current He-Ion Control by Bounce Resonant ULF Waves
Abstract: Ring current energy He-ion (∼65 keV to ∼520 keV) differential flux data from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft show considerable variability during quiet solar wind and geomagnetic time periods. Such variability is apparent from orbit to orbit (∼9 hours) of the spacecraft and is observed to be ∼50–100% of the nominal flux. Using data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument, also aboard the Van Allen Probes spacecraft, we identify that a dominant source of this variability is from ULF waveforms with periods of 10's of sec. These periods correspond to the bounce resonant timescales of the ring current He-ions being measured by RBSPICE. A stat. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA023958 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA023958/full
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Authors: Aseev N. A., Shprits Y Y, Drozdov A. Y., Kellerman A. C., Usanova M. E., et al.
Title: Signatures of Ultrarelativistic Electron Loss in the Heart of the Outer Radiation Belt Measured by Van Allen Probes
Abstract: Up until recently, signatures of the ultrarelativistic electron loss driven by electromagnetic ion cyclotron (EMIC) waves in the Earth's outer radiation belt have been limited to direct or indirect measurements of electron precipitation or the narrowing of normalized pitch angle distributions in the heart of the belt. In this study, we demonstrate additional observational evidence of ultrarelativistic electron loss that can be driven by resonant interaction with EMIC waves. We analyzed the profiles derived from Van Allen Probe particle data as a function of time and three adiabatic invariants between 9 October and 29 November 2012. New local minimums in the profiles are accompanied by the narrowing of normalized pitch angle distributions and ground-based detection of EMIC waves. Such a cor. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024485 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024485/full
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Authors: Hudson Mary, Jaynes Allison, Kress Brian, Li Zhao, Patel Maulik, et al.
Title: Simulated prompt acceleration of multi-MeV electrons by the 17 March 2015 interplanetary shock
Abstract: Prompt enhancement of relativistic electron flux at L = 3−5 has been reported from Van Allen Probes Relativistic Electron Proton Telescope (REPT) measurements associated with the 17 March 2015 interplanetary shock compression of the dayside magnetosphere. Acceleration by ∼ 1 MeV is inferred on less than a drift time scale as seen in prior shock compression events, which launch a magetosonic azimuthal electric field impulse tailward. This impulse propagates from the dayside around the flanks accelerating electrons in drift resonance at the dusk flank. Such longitudinally localized acceleration events produce a drift echo signature which was seen at >1 MeV energy on both Van Allen Probe spacecraft, with sustained observations by Probe B outbound at L = 5 at 2100 MLT at the time of impuls. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024445 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024445/full
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Authors: Jahn J -M, Goldstein J, Reeves G D, Fernandes P. A., Skoug R M, et al.
Title: The Warm Plasma Composition in the Inner Magnetosphere during 2012-2015
Abstract: Ionospheric heavy ions play an important role in the dynamics of Earth's magnetosphere. The greater mass and gyro radius of ionospheric oxygen differentiates its behavior from protons at the same energies. Oxygen may have an impact on tail reconnection processes, and it can at least temporarily dominate the energy content of the ring current during geomagnetic storms. At sub-keV energies, multi-species ion populations in the inner magnetosphere form the warm plasma cloak, occupying the energy range between the plasmasphere and the ring current. Lastly, cold lighter ions from the mid-latitude ionosphere create the co-rotating plasmasphere whose outer regions can interact with the plasma cloak, plasma sheet, ring current, and outer electron belt. In this paper we present a statistical view o. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024183 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024183/full
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Authors: Souza V. M., Lopez R. E., Jauer P. R., Sibeck D G, Pham K., et al.
Title: Acceleration of radiation belt electrons and the role of the average interplanetary magnetic field B z component in high speed streams
Abstract: In this study we examine the recovery of relativistic radiation belt electrons on November 15-16, 2014, after a previous reduction in the electron flux resulting from the passage of a Corotating Interaction Region (CIR). Following the CIR, there was a period of high-speed streams characterized by large, nonlinear fluctuations in the interplanetary magnetic field (IMF) components. However, the outer radiation belt electron flux remained at a low level for several days before it increased in two major steps. The first increase is associated with the IMF background field turning from slightly northward on average, to slightly southward on average. The second major increase is associated with an increase in the solar wind velocity during a period of southward average IMF background field. We p. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024187 Available at: onlinelibrary.wiley.com/doi/10.1002/2017JA024187/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: 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: Cattell C., Breneman A., Colpitts C., Dombeck J., Thaller S., et al.
Title: Dayside response of the magnetosphere to a small shock compression: Van Allen Probes, Magnetospheric MultiScale, and GOES-13
Abstract: Observations from Magnetospheric MultiScale (~8 Re) and Van Allen Probes (~5 and 4 Re) show that the initial dayside response to a small interplanetary shock is a double-peaked dawnward electric field, which is distinctly different from the usual bipolar (dawnward and then duskward) signature reported for large shocks. The associated ExB flow is radially inward. The shock compressed the magnetopause to inside 8 Re, as observed by MMS, with a speed that is comparable to the ExB flow. The magnetopause speed and the ExB speeds were significantly less than the propagation speed of the pulse from MMS to the Van Allen Probes and GOES-13, which is consistent with the MHD fast mode. There were increased fluxes of energetic electrons up to several MeV. Signatures of drift echoes and response to ULF. . .
Date: 08/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074895 Available at: onlinelibrary.wiley.com/doi/10.1002/2017GL074895/full
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Authors: Cohen Ian J., Mitchell Donald G., Kistler Lynn M., Mauk Barry H., Anderson Brian J., et al.
Title: Dominance of high energy (>150 keV) heavy ion intensities in Earth's middle to outer magnetosphere
Abstract: Previous observations have driven the prevailing assumption in the field that energetic ions measured by an instrument using a bare solid state detector (SSD) are predominantly protons. However, new near-equatorial energetic particle observations obtained between 7 and 12 RE during Phase 1 of the Magnetospheric Multiscale (MMS) mission challenge the validity of this assumption. In particular, measurements by the Energetic Ion Spectrometer (EIS) instruments have revealed that the intensities of heavy ion species (specifically oxygen and helium) dominate those of protons at energies math formula150-220 keV in the middle to outer (>7 RE) magnetosphere. Given that relative composition measurements can drift as sensors degrade in gain, quality cross-calibration agreement between EIS observation. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024351 Available at: onlinelibrary.wiley.com/doi/10.1002/2017JA024351/full
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Authors: Drozdov A. Y., Shprits Y Y, Usanova M. E., Aseev N. A., Kellerman A. C., et al.
Title: EMIC wave parameterization in the long-term VERB code simulation
Abstract: Electromagnetic ion cyclotron (EMIC) waves play an important role in the dynamics of ultrarelativistic electron population in the radiation belts. However, as EMIC waves are very sporadic, developing a parameterization of such wave properties is a challenging task. Currently, there are no dynamic, activity-dependent models of EMIC waves that can be used in the long-term (several months) simulations, which makes the quantitative modeling of the radiation belt dynamics incomplete. In this study, we investigate Kp, Dst, and AE indices, solar wind speed, and dynamic pressure as possible parameters of EMIC wave presence. The EMIC waves are included in the long-term simulations (1 year, including different geomagnetic activity) performed with the Versatile Electron Radiation Belt code, and we co. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024389 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024389/full
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Authors: Pich Maria de Soria-S, Jun Insoo, and Evans Robin
Title: Empirical radiation belt models: Comparison with in-situ data and implications for environment definition
Abstract: The empirical AP8/AE8 model has been the de-facto Earth's radiation belts engineering reference for decades. The need from the community for a better model incubated the development of AP9/AE9/SPM, which addresses several shortcomings of the old model. We provide additional validation of AP9/AE9 by comparing in-situ electron and proton data from Jason-2, POES, and the Van Allen Probes spacecraft with the 5th, 50th, and 95th percentiles from AE9/AP9 and with the model outputs from AE8/AP8. The relatively short duration of Van Allen Probes and Jason-2 missions means that their measurements are most certainly the result of specific climatological conditions. In LEO, the Jason-2 proton flux is better reproduced by AP8 compared to AP9, while the POES electron data are well enveloped by AE9 5th . . .
Date: 08/2017 Publisher: Space Weather DOI: 10.1002/2017SW001612 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017SW001612/full
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Authors: Ren Jie, Zong Q. G., Miyoshi Y, Zhou X. Z., Wang Y. F., et al.
Title: Low-energy (< 200 eV) electron acceleration by ULF waves in the plasmaspheric boundary layer: Van Allen Probes observation
Abstract: We report observational evidence of cold plamsmaspheric electron (< 200 eV) acceleration by ultra-low-frequency (ULF) waves in the plasmaspheric boundary layer on 10 September 2015. Strongly enhanced cold electron fluxes in the energy spectrogram were observed along with second harmonic mode waves with a period of about 1 minute which lasted several hours during two consecutive Van Allen Probe B orbits. Cold electron (<200 eV) and energetic proton (10-20 keV) bi-directional pitch angle signatures observed during the event are suggestive of the drift-bounce resonance mechanism. The correlation between enhanced energy fluxes and ULF waves leads to the conclusions that plasmaspheric dynamics is strongly affected by ULF waves. Van Allen Probe A and B, GOES 13, GOES 15 and MMS 1 observations su. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024316 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024316/full
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Authors: Fernandes Philip A., Larsen Brian A., Thomsen Michelle F., Skoug Ruth M., Reeves Geoffrey D, et al.
Title: The plasma environment inside geostationary orbit: A Van Allen Probes HOPE survey
Abstract: The two full precessions in local time completed by the Van Allen Probes enable global specification of the near-equatorial inner magnetosphere plasma environment. Observations by the Helium-Oxygen-Proton-Electron (HOPE) mass spectrometers provide detailed insight into the global spatial distribution of electrons, H+, He+, and O+. Near-equatorial omnidirectional fluxes and abundance ratios at energies 0.1–30 keV are presented for 2 ≤ L ≤ 6 as a function of L shell, magnetic local time (MLT), and geomagnetic activity. We present a new tool built on the UBK modeling technique for classifying plasma sheet particle access to the inner magnetosphere. This new tool generates access maps for particles of constant energy for more direct comparison with in situ measurements, rather than the t. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024160 Available at: onlinelibrary.wiley.com/doi/10.1002/2017JA024160/full
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Authors: Mozer F S, Agapitov O. V., Hull A., Lejosne S., and Vasko I. Y.
Title: Pulsating auroras produced by interactions of electrons and time domain structures
Abstract: Previous evidence has suggested that either lower band chorus waves or kinetic Alfven waves scatter equatorial kilovolt electrons that propagate to lower altitudes where they precipitate or undergo further low-altitude scattering to make pulsating auroras. Recently, time domain structures (TDSs) were shown, both theoretically and experimentally, to efficiently scatter equatorial electrons. To assess the relative importance of these three mechanisms for production of pulsating auroras, 11 intervals of equatorial THEMIS data and a 4 h interval of Van Allen Probe measurements have been analyzed. During these events, lower band chorus waves produced only negligible modifications of the equatorial electron distributions. During the several TDS events, the equatorial 0.1–3 keV electrons became. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024223 Available at: onlinelibrary.wiley.com/doi/10.1002/2017JA024223/full
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Authors: Su Zhenpeng, Gao Zhonglei, Zheng Huinan, Wang Yuming, Wang Shui, et al.
Title: Rapid loss of radiation belt relativistic electrons by EMIC waves
Abstract: How relativistic electrons are lost is an important question surrounding the complex dynamics of the Earth's outer radiation belt. Radial loss to the magnetopause and local loss to the atmosphere are two main competing paradigms. Here, on the basis of the analysis of a radiation belt storm event on 27 February 2014, we present new evidence for the EMIC wave-driven local precipitation loss of relativistic electrons in the heart of the outer radiation belt. During the main phase of this storm, the radial profile of relativistic electron phase space density was quasi-monotonic, qualitatively inconsistent with the prediction of radial loss theory. The local loss at low L-shells was required to prevent the development of phase space density peak resulting from the radial loss process at high L-. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024169 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024169/full
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Authors: Allen R. C., Livi S. A., Vines S. K., Goldstein J, Cohen I., et al.
Title: Storm time empirical model of O + and O 6+ distributions in the magnetosphere
Abstract: Recent studies have utilized different charge states of oxygen ions as a tracer for the origins of plasma populations in the magnetosphere of Earth, using O+ as an indicator of ionospheric-originating plasma and O6+ as an indicator of solar wind-originating plasma. These studies have correlated enhancements in O6+ to various solar wind and geomagnetic conditions to characterize the dominant solar wind injection mechanisms into the magnetosphere but did not include analysis of the temporal evolution of these ions. A sixth-order Fourier expansion model based empirically on a superposed epoch analysis of geomagnetic storms observed by Polar is presented in this study to provide insight into the evolution of both ionospheric-originating and solar wind-originating plasma throughout geomagnetic . . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024245 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024245/full
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Authors: Lejosne ène, and Mozer F S
Title: Sub-Auroral Polarization Stream (SAPS) duration as determined from Van Allen Probe successive electric drift measurements
Abstract: We examine a characteristic feature of the magnetosphere-ionosphere coupling, namely, the persistent and latitudinally narrow bands of rapid westward ion drifts called the Sub-Auroral Polarization Streams (SAPS). Despite countless works on SAPS, information relative to their durations is lacking. Here, we report on the first statistical analysis of more than 200 near-equatorial SAPS observations based on more than two years of Van Allen Probe electric drift measurements. First, we present results relative to SAPS radial locations and amplitudes. Then, we introduce two different ways to estimate SAPS durations. In both cases, SAPS activity is estimated to last for about nine hours on average. However, our estimates for SAPS duration are limited either by the relatively long orbital periods . . .
Date: 08/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074985 Available at: http://http://onlinelibrary.wiley.com/doi/10.1002/2017GL074985/full
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Authors: Xiang Zheng, Tu Weichao, Li Xinlin, Ni Binbin, Morley S. K., et al.
Title: Understanding the Mechanisms of Radiation Belt Dropouts Observed by Van Allen Probes
Abstract: To achieve a better understanding of the dominant loss mechanisms for the rapid dropouts of radiation belt electrons, three distinct radiation belt dropout events observed by Van Allen Probes are comprehensively investigated. For each event, observations of the pitch angle distribution of electron fluxes and electromagnetic ion cyclotron (EMIC) waves are analyzed to determine the effects of atmospheric precipitation loss due to pitch angle scattering induced by EMIC waves. Last closed drift shells (LCDS) and magnetopause standoff position are obtained to evaluate the effects of magnetopause shadowing loss. Evolution of electron phase space density (PSD) versus L* profiles and the μ and K (first and second adiabatic invariants) dependence of the electron PSD drops are calculated to further. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024487 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024487/full
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Authors: Su Zhenpeng, Wang Geng, Liu Nigang, Zheng Huinan, Wang Yuming, et al.
Title: Direct observation of generation and propagation of magnetosonic waves following substorm injection
Abstract: Magnetosonic whistler mode waves play an important role in the radiation belt electron dynamics. Previous theory has suggested that these waves are excited by the ring distributions of hot protons and can propagate radially and azimuthally over a broad spatial range. However, because of the challenging requirements on satellite locations and data-processing techniques, this theory was difficult to validate directly. Here we present some experimental tests of the theory on the basis of Van Allen Probes observations of magnetosonic waves following substorm injections. At higher L-shells with significant substorm injections, the discrete magnetosonic emission lines started approximately at the proton gyrofrequency harmonics, qualitatively consistent with the prediction of linear proton Bernst. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074362 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL074362/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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Authors: Yu Xiongdong, Yuan Zhigang, Huang Shiyong, Wang Dedong, Li Haimeng, et al.
Title: EMIC waves covering wide L shells: MMS and Van Allen Probes observations
Abstract: During 04:45:00–08:15:00 UT on 13 September in 2015, a case of Electromagnetic ion cyclotron (EMIC) waves covering wide L shells (L = 3.6–9.4), observed by the Magnotospheric Multiscale 1 (MMS1) are reported. During the same time interval, EMIC waves observed by Van Allen Probes A (VAP-A) only occurred just outside the plasmapause. As the Van Allen Probes moved outside into a more tenuous plasma region, no intense waves were observed. Combined observations of MMS1 and VAP-A suggest that in the terrestrial magnetosphere, an appropriately dense background plasma would make contributions to the growth of EMIC waves in lower L shells, while the ion anisotropy, driven by magnetospheric compression, might play an important role in the excitation of EMIC waves in higher L shells. These EMIC w. . .
Date: 07/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA023982 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA023982/full
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Authors: Yuan Zhigang, Yu Xiongdong, Huang Shiyong, Wang Dedong, and Funsten Herbert O.
Title: In situ observations of magnetosonic waves modulated by background plasma density
Abstract: We report in situ observations by the Van Allen Probe mission that magnetosonic (MS) waves are clearly relevant to appear relevant to the background plasma number density. As the satellite moved across dense and tenuous plasma alternatively, MS waves occurred only in lower density region. As the observed protons with ‘ring’ distributions provide free energy, local linear growth rates are calculated and show that magnetosonic waves can be locally excited in tenuous plasma. With variations of the background plasma density, the temporal variations of local wave growth rates calculated with the observed proton ring distributions, show a remarkable agreement with those of the observed wave amplitude. Therefore, the paper provides a direct proof that background plasma densities can modulate . . .
Date: 07/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074681 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL074681/full
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Authors: Lejosne ène, Maus Stefan, and Mozer F S
Title: Model-observation comparison for the geographic variability of the plasma electric drift in the Earth's innermost magnetosphere
Abstract: Plasmaspheric rotation is known to lag behind Earth rotation. The causes for this corotation lag are not yet fully understood. We have used more than two years of Van Allen Probe observations to compare the electric drift measured below L~2 with the predictions of a general model. In the first step, a rigid corotation of the ionosphere with the solid Earth was assumed in the model. The results of the model-observation comparison are twofold: (1) radially, the model explains the average observed geographic variability of the electric drift; (2) azimuthally, the model fails to explain the full amplitude of the observed corotation lag. In the second step, ionospheric corotation was modulated in the model by thermospheric winds, as given by the latest version of the Horizontal Wind Model (HWM1. . .
Date: 07/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074862 Available at: onlinelibrary.wiley.com/doi/10.1002/2017GL074862/full
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Authors: Chaston C. C., Bonnell J. W., Wygant J R, Reeves G D, Baker D N, et al.
Title: Radial transport of radiation belt electrons in kinetic field-line resonances
Abstract: A representative case study from the Van Allen Probes during a geomagnetic storm recovery phase reveals enhanced electron fluxes at intermediate pitch angles over energies from ~100 keV to 5 MeV coincident with broadband low frequency electromagnetic waves. The statistical properties of these waves are used to build a model for radial diffusion via drift-bounce resonances in kinetic Alfvén eigenmodes/kinetic field-line resonances. Estimated diffusion coefficients indicate timescales for radial transport of the order of hours in storm-time events at energies from <100 keV to MeVs over equatorial pitch angles from the edge of the loss cone to nearly perpendicular to the geomagnetic field. The correlation of kinetic resonances with electron depletions and enhancements during storm main phase. . .
Date: 07/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074587 Available at: onlinelibrary.wiley.com/doi/10.1002/2017GL074587/full
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Authors: Hao Y. X., Zong Q.-G., Zhou X.-Z., Rankin R, Chen X. R., et al.
Title: Relativistic electron dynamics produced by azimuthally localized poloidal mode ULF waves: Boomerang-shaped pitch angle evolutions
Abstract: We present an analysis of “boomerang-shaped” pitch angle evolutions of outer radiation belt relativistic electrons observed by the Van Allen Probes after the passage of an interplanetary shock on June 7th, 2014. The flux at different pitch angles is modulated by Pc5 waves, with equatorially mirroring electrons reaching the satellite first. For 90∘ pitch angle electrons, the phase change of the flux modulations across energy exceeds 180∘, and increasingly tilts with time. Using estimates of the arrival time of particles of different pitch angles at the spacecraft location, a scenario is investigated in which shock-induced ULF waves interact with electrons through the drift resonance mechanism in a localized region westward of the spacecraft. Numerical calculations on particle energy. . .
Date: 07/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074006 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL074006/full
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Authors: Malaspina David M., Jaynes Allison N, Hospodarsky George, Bortnik Jacob, Ergun Robert E, et al.
Title: Statistical Properties of Low Frequency Plasmaspheric Hiss
Abstract: Plasmaspheric hiss is an important wave mode for the dynamics of inner terrestrial magnetosphere plasma populations. It acts to scatter high energy electrons out of trapped orbits about Earth and into the atmosphere, defining the inner edge of the radiation belts over a range of energies. A low-frequency component of hiss was recently identified and is important for its ability to interact with higher energy electrons compared to typically considered hiss frequencies. This study compares the statistical properties of low and high frequency plasmaspheric hiss in the terrestrial magnetosphere, demonstrating that they are statistically distinct wave populations. Low frequency hiss shows different behavior in frequency space, different spatial localization (in magnetic local time and radial di. . .
Date: 07/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024328 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024328/full
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Authors: Shen Xiao-Chen, Hudson Mary, Jaynes Allison, Shi Quanqi, Tian Anmin, et al.
Title: Statistical study of the storm-time radiation belt evolution during Van Allen Probes era: CME- versus CIR-driven storms
Abstract: CME- or CIR-driven storms can change the electron distributions in the radiation belt dramatically, which can in turn affect the spacecraft in this region or induce geomagnetic effects. The Van Allen Probes twin spacecraft, launched on 30 August 2012, orbit near the equatorial plane and across a wide range of L∗ with apogee at 5.8 RE and perigee at 620 km. Electron data from Van Allen Probes MagEIS and REPT instruments have been binned every six hours at L∗=3 (defined as 2.5 Date: 07/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024100 Available at: onlinelibrary.wiley.com/doi/10.1002/2017JA024100/full
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Authors: Ripoll J.-F., Santol?k O., Reeves G., Kurth W S, Denton M., et al.
Title: Effects of whistler mode hiss waves in March 2013
Abstract: 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 hours 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 aga. . .
Date: 06/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024139 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024139/full
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Authors: Sarris Theodore E., Li Xinlin, Temerin Michael, Zhao Hong, Califf Sam, et al.
Title: On the Relationship Between Electron Flux Oscillations and ULF Wave-Driven Radial Transport
Abstract: The objective of this study is to investigate the relationship between the levels of electron flux oscillations and radial diffusion for different Phase Space Density (PSD) gradients, through observation and particle tracing simulations under the effect of model Ultra Low Frequency (ULF) fluctuations. This investigation aims to demonstrate that electron flux oscillation is associated with and could be used as an indicator of ongoing radial diffusion. To this direction, flux oscillations are observed through the Van Allen Probes’ MagEIS energetic particle detector; subsequently, flux oscillations are produced in a particle tracing model that simulates radial diffusion by using model magnetic and electric field fluctuations that are approximating measured magnetic and electric field fluctu. . .
Date: 06/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023741 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023741/full
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Authors: Hwang J., Shin D. K., Yoon P. H., Kurth W S, Larsen B A, et al.
Title: Roles of hot electrons in generating upper-hybrid waves in the earth's radiation belt
Abstract: Electrostatic fluctuations near upper-hybrid frequency, which are sometimes accompanied by multiple-harmonic electron cyclotron frequency bands above and below the upper-hybrid frequency, are common occurrences in the Earth's radiation belt, as revealed through the twin Van Allen Probe spacecrafts. It is customary to use the upper-hybrid emissions for estimating the background electron density, which in turn can be used to determine the plasmapause locations, but the role of hot electrons in generating such fluctuations has not been discussed in detail. The present paper carries out detailed analyses of data from the Waves instrument, which is part of the Electric and Magnetic Field Instrument Suite and Integrated Science suite onboard the Van Allen Probes. Combined with the theoretical ca. . .
Date: 06/2017 Publisher: Physics of Plasmas Pages: 062904 DOI: 10.1063/1.4984249 Available at: http://aip.scitation.org/doi/10.1063/1.4984249
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Authors: Li Zhao, Hudson Mary, Patel Maulik, Wiltberger Michael, Boyd Alex, et al.
Title: ULF Wave Analysis and Radial Diffusion Calculation Using a Global MHD Model for the 17 March 2013 and 2015 Storms
Abstract: The 17 March 2015 St. Patrick's Day Storm is the largest geomagnetic storm to date of Solar Cycle 24, with a Dst of -223 nT. The magnetopause moved inside geosynchronous orbit under high solar wind dynamic pressure and strong southward IMF Bz causing loss, however a subsequent drop in pressure allowed for rapid rebuilding of the radiation belts. The 17 March 2013 storm also shows similar effects on outer zone electrons: first a rapid dropout due to inward motion of the magnetopause followed by rapid increase in flux above the pre-storm level early in the recovery phase and a slow increase over the next 12 days. These phases can be seen in temporal evolution of the electron phase space density measured by the ECT instruments on Van Allen Probes. Using the Lyon-Fedder-Mobarry global MHD m. . .
Date: 06/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023846 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023846/full
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Authors: Yang Xiaochao, Ni Binbin, Yu Jiang, Zhang Yang, Zhang Xiaoxin, et al.
Title: Unusual refilling of the slot region between the Van Allen radiation belts from November 2004 to January 2005
Abstract: Using multisatellite measurements, a uniquely strong and long-lived relativistic electron slot region refilling event from November 2004 to January 2005 is investigated. This event occurred under remarkable interplanetary and magnetospheric conditions. Both empirically modeled and observationally estimated plasmapause locations demonstrate that the plasmasphere eroded significantly prior to the enhancement phase of this event. The estimated diffusion coefficients indicate that the radial diffusion due to ULF waves is insufficient to account for the observed enhancement of slot region electrons. However, the diffusion coefficients evaluated using the distribution of chorus wave intensities derived from low-altitude POES electron observations indicate that the local acceleration induced by c. . .
Date: 06/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023204 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023204/full
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