Biblio

Found 643 results
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2017
Authors: Cohen Ross, Gerrard Andrew J., Lanzerotti Louis J., Soto-Chavez A. R., Kim Hyomin, et al.
Title: Climatology of high-β plasma measurements in Earth's inner magnetosphere
Abstract: Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high-resolution measurements of Earth's ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high-beta (β) plasma events (defined here as β > 1) as measured by the RBSPICE instrument in the ∼45 keV to ∼600 keV proton energy range in the inner magnetosphere (L < 5.8) has been constructed. In this paper we report this climatology of such high-β plasma occurrences, durations, and their general characteristics. Specifically, we show that most high-β events in the RBSPICE energy range are associated with postdusk/premidni. . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022513 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA022513
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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: Kronberg E. A., Grigorenko E. E., Turner D. L., Daly P. W., Khotyaintsev Y., et al.
Title: Comparing and contrasting dispersionless injections at geosynchronous orbit during a substorm event
Abstract: Particle injections in the magnetosphere transport electrons and ions from the magnetotail to the radiation belts. Here we consider generation mechanisms of “dispersionless” injections, namely, those with simultaneous increase of the particle flux over a wide energy range. In this study we take advantage of multisatellite observations which simultaneously monitor Earth's magnetospheric dynamics from the tail toward the radiation belts during a substorm event. Dispersionless injections are associated with instabilities in the plasma sheet during the growth phase of the substorm, with a dipolarization front at the onset and with magnetic flux pileup during the expansion phase. They show different spatial spread and propagation characteristics. Injection associated with the dipolarization. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023551 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023551/full
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Authors: Demekhov A. G., Manninen J., ík O., and Titova E. E.
Title: Conjugate Ground-Spacecraft Observations of VLF Chorus Elements
Abstract: We present results of simultaneous observations of VLF chorus elements at the ground-based station Kannuslehto in Northern Finland and on board Van Allen Probe A. Visual inspection and correlation analysis of the data reveal one-to-one correspondence of several (at least 12) chorus elements following each other in a sequence. Poynting flux calculated from electromagnetic fields measured by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probe A shows that the waves propagate at small angles to the geomagnetic field and oppositely to its direction, that is, from northern to southern geographic hemisphere. The spacecraft was located at L≃4.1 at a geomagnetic latitude of −12.4∘ close to the plasmapause and inside a localized density . . .
Date: 12/2017 Publisher: Geophysical Research Letters Pages: 11,735 - 11,744 DOI: 10.1002/2017GL076139 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL076139/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: Goldstein J, Angelopoulos V, De Pascuale S., Funsten H O, Kurth W S, et al.
Title: Cross-scale observations of the 2015 St. Patrick's day storm: THEMIS, Van Allen Probes, and TWINS
Abstract: We present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick's Day) storm, by Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes (Radiation Belt Storm Probes), and Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS), plus upstream ACE/Wind solar wind data. THEMIS crossed the bow shock or magnetopause 22 times and observed the magnetospheric compression that initiated the storm. Empirical models reproduce these boundary locations within 0.7 RE. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 RE. Before the storm, Van Allen Probes measured quiet double-nose proton spectra in the region of corotating cold plasma. About 15 min after a 0605 UT dayside sout. . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics Pages: 368 - 392 DOI: 10.1002/jgra.v122.110.1002/2016JA023173 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023173/full
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Authors: Goldstein J., Angelopoulos V., De Pascuale S., Funsten H. O., Kurth W. S., et al.
Title: Cross-scale observations of the 2015 St. Patrick's day storm: THEMIS, Van Allen Probes, and TWINS
Abstract: We present cross-scale magnetospheric observations of the 17 March 2015 (St. Patrick's Day) storm, by Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes (Radiation Belt Storm Probes), and Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS), plus upstream ACE/Wind solar wind data. THEMIS crossed the bow shock or magnetopause 22 times and observed the magnetospheric compression that initiated the storm. Empirical models reproduce these boundary locations within 0.7 RE. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 RE. Before the storm, Van Allen Probes measured quiet double-nose proton spectra in the region of corotating cold plasma. About 15 min after a 0605 UT dayside sout. . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023173 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023173
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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: Drozdov A. Y., Shprits Y Y, Aseev N. A., Kellerman A. C., and Reeves G D
Title: Dependence of radiation belt simulations to assumed radial diffusion rates tested for two empirical models of radial transport
Abstract: Radial diffusion is one of the dominant physical mechanisms that drives acceleration and loss of the radiation belt electrons, which makes it very important for nowcasting and forecasting space weather models. We investigate the sensitivity of the two parameterizations of the radial diffusion of Brautigam and Albert (2000) and Ozeke et al. (2014) on long-term radiation belt modeling using the Versatile Electron Radiation Belt (VERB). Following Brautigam and Albert (2000) and Ozeke et al. (2014), we first perform 1-D radial diffusion simulations. Comparison of the simulation results with observations shows that the difference between simulations with either radial diffusion parameterization is small. To take into account effects of local acceleration and loss, we perform 3-D simulations, in. . .
Date: 01/2017 Publisher: Space Weather Pages: 150 - 162 DOI: 10.1002/swe.v15.110.1002/2016SW001426 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016SW001426/full
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Authors: Kim Kyung-Chan, and Shprits Yuri
Title: Dependence of the amplitude of magnetosonic waves on the solar wind and AE index using Van Allen Probes
Abstract: We present the dependence of the magnetosonic wave amplitudes both outside and inside the plasmapause on the solar wind and AE index using Van Allen Probe-A spacecraft during the time period of 1 October 2012 to 31 December 2015, based on a correlation and regression analysis. Solar wind parameters considered are the southward interplanetary magnetic field (IMF BS), solar wind number density (NSW), and bulk speed (VSW). We find that the wave amplitudes outside (inside) the plasmapause are well correlated with the preceding AE, IMF BS, and NSW with time delays, each corresponding to 2–3 h (3–4 h), 4–5 h (3–4 h), and 2–3 h (8–9 h), while the correlation with VSW is ambiguous both inside and outside the plasmapause. As measured by the correlation coefficient, the IMF BS is the mos. . .
Date: 05/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024094 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024094/full
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Authors: Vasko I. Y., Agapitov O. V., Mozer F S, Artemyev A. V., Krasnoselskikh V. V., et al.
Title: Diffusive scattering of electrons by electron holes around injection fronts
Abstract: Van Allen Probes have detected nonlinear electrostatic spikes around injection fronts in the outer radiation belt. These spikes include electron holes (EH), double layers, and more complicated solitary waves. We show that EHs can efficiently scatter electrons due to their substantial transverse electric fields. Although the electron scattering driven by EHs is diffusive, it cannot be evaluated via the standard quasi-linear theory. We derive analytical formulas describing local electron scattering by a single EH and verify them via test particle simulations. We show that the most efficiently scattered are gyroresonant electrons (crossing EH on a time scale comparable to the local electron gyroperiod). We compute bounce-averaged diffusion coefficients and demonstrate their dependence on the . . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023337 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023337/full
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Authors: 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: 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: 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: 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: 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: Vasko I. Y., Agapitov O. V., Mozer F S, Bonnell J. W., Artemyev A. V., et al.
Title: Electron-acoustic solitons and double layers in the inner magnetosphere
Abstract: The Van Allen Probes observe generally two types of electrostatic solitary waves (ESW) contributing to the broadband electrostatic wave activity in the nightside inner magnetosphere. ESW with symmetric bipolar parallel electric field are electron phase space holes. The nature of ESW with asymmetric bipolar (and almost unipolar) parallel electric field has remained puzzling. To address their nature, we consider a particular event observed by Van Allen Probes to argue that during the broadband wave activity electrons with energy above 200 eV provide the dominant contribution to the total electron density, while the density of cold electrons (below a few eV) is less than a few tenths of the total electron density. We show that velocities of the asymmetric ESW are close to velocity of electron. . .
Date: 05/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074026 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL074026/full
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Authors: 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: Blum L. W., Bonnell J. W., Agapitov O., Paulson K., and Kletzing C.
Title: EMIC wave scale size in the inner magnetosphere: Observations from the dual Van Allen Probes
Abstract: Estimating the spatial scales of electromagnetic ion cyclotron (EMIC) waves is critical for quantifying their overall scattering efficiency and effects on thermal plasma, ring current, and radiation belt particles. Using measurements from the dual Van Allen Probes in 2013–2014, we characterize the spatial and temporal extents of regions of EMIC wave activity and how these depend on local time and radial distance within the inner magnetosphere. Observations are categorized into three types—waves observed by only one spacecraft, waves measured by both spacecraft simultaneously, and waves observed by both spacecraft with some time lag. Analysis reveals that dayside (and H+ band) EMIC waves more frequently span larger spatial areas, while nightside (and He+ band) waves are more often loc. . .
Date: 02/2017 Publisher: Geophysical Research Letters Pages: 1227 - 1233 DOI: 10.1002/2016GL072316 Available at: http://doi.wiley.com/10.1002/2016GL072316
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Title: EMIC wave scale size in the inner magnetosphere: Observations from the dual Van Allen Probes
Abstract: Estimating the spatial scales of electromagnetic ion cyclotron (EMIC) waves is critical for quantifying their overall scattering efficiency and effects on thermal plasma, ring current, and radiation belt particles. Using measurements from the dual Van Allen Probes in 2013–2014, we characterize the spatial and temporal extents of regions of EMIC wave activity and how these depend on local time and radial distance within the inner magnetosphere. Observations are categorized into three types—waves observed by only one spacecraft, waves measured by both spacecraft simultaneously, and waves observed by both spacecraft with some time lag. Analysis reveals that dayside (and H+ band) EMIC waves more frequently span larger spatial areas, while nightside (and He+ band) waves are more often loc. . .
Date: 01/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL072316 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL072316
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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: 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: Andreeva V. A., and Tsyganenko N A
Title: Empirical modeling of the quiet and storm-time geosynchronous magnetic field
Abstract: A dynamical empirical model of the near-geosynchronous magnetic field has been constructed, based on a recently developed RBF approach and a multi-year set of spacecraft data taken by THEMIS, Polar, Cluster, and Van Allen Probes missions including 133 geomagnetic storms in the time interval between 1996 and 2016. The model describes the field as a function of Cartesian solar-magnetic coordinates, dipole tilt angle, solar wind ram pressure, and of a set of dynamic variables representing the response of the magnetosphere to the external driving/loading during the active phase of a space weather event, followed by the internal relaxation/dissipation during the storm recovery. In terms of the disturbance level, the model's validity range extends to intense storms with peak Sym-H values down to. . .
Date: 12/2017 Publisher: Space Weather DOI: 10.1002/2017SW001684 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017SW001684/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: Oyama S., Kero A., Rodger C. J., Clilverd M A, Miyoshi Y, et al.
Title: Energetic electron precipitation and auroral morphology at the substorm recovery phase
Abstract: It is well known that auroral patterns at the substorm recovery phase are characterized by diffuse or patch structures with intensity pulsation. According to satellite measurements and simulation studies, the precipitating electrons associated with these aurorae can reach or exceed energies of a few hundreds of keV through resonant wave-particle interactions in the magnetosphere. However, because of difficulty of simultaneous measurements, the dependency of energetic electron precipitation (EEP) on auroral morphological changes in the mesoscale has not been investigated to date. In order to study this dependency, we have analyzed data from the European Incoherent Scatter (EISCAT) radar, the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) riometer, collocated cameras, ground-based m. . .
Date: 05/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023484 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023484/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: 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: Takahashi Kazue, Denton Richard E., Kurth William, Kletzing Craig, Wygant John, et al.
Title: Externally driven plasmaspheric ULF waves observed by the Van Allen Probes
Abstract: We analyze data acquired by the Van Allen Probes on 8 November 2012, during a period of extended low geomagnetic activity, to gain new insight into plasmaspheric ultralow frequency (ULF) waves. The waves exhibited strong spectral power in the 5–40 mHz band and included multiharmonic toroidal waves visible up to the eleventh harmonic, unprecedented in the plasmasphere. During this wave activity, the interplanetary magnetic field cone angle was small, suggesting that the waves were driven by broadband compressional ULF waves originating in the foreshock region. This source mechanism is supported by the tailward propagation of the compressional magnetic field perturbations at a phase velocity of a few hundred kilometers per second that is determined by the cross-phase analysis of data from . . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020373 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2014JA020373
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Authors: Xiao Fuliang, Liu Si, Tao Xin, Su Zhenpeng, Zhou Qinghua, et al.
Title: Generation of extremely low frequency chorus in Van Allen radiation belts
Abstract: Recent studies have shown that chorus can efficiently accelerate the outer radiation belt electrons to relativistic energies. Chorus, previously often observed above 0.1 equatorial electron gyrofrequency fce, was generated by energetic electrons originating from Earth's plasma sheet. Chorus below 0.1 fce has seldom been reported until the recent data from Van Allen Probes, but its origin has not been revealed so far. Because electron resonant energy can approach the relativistic level at extremely low frequency, relativistic effects should be considered in the formula for whistler mode wave growth rate. Here we report high-resolution observations during the 14 October 2014 small storm and firstly demonstrate, using a fully relativistic simulation, that electrons with the high-energy tail p. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023561 Available at: http://doi.wiley.com/10.1002/2016JA023561
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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: Zhou Qinghua, Xiao Fuliang, Yang Chang, Liu Si, He Yihua, et al.
Title: Generation of lower and upper bands of electrostatic electron cyclotron harmonic waves in the Van Allen radiation belts
Abstract: Electrostatic electron cyclotron harmonic (ECH) waves generated by the electron loss cone distribution can produce efficient scattering loss of plasma sheet electrons, which has a significant effect on the dynamics in the outer magnetosphere. Here we report two ECH emission events around the same location L≈ 5.7–5.8, MLT ≈ 12 from Van Allen Probes on 11 February (event A) and 9 January 2014 (event B), respectively. The spectrum of ECH waves was centered at the lower half of the harmonic bands during event A, but the upper half during event B. The observed electron phase space density in both events is fitted by the subtracted bi-Maxwellian distribution, and the fitting functions are used to evaluate the local growth rates of ECH waves based on a linear theory for homogeneous plasmas.. . .
Date: 05/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073051 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL073051/full
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Authors: Le G., Chi P. J., Strangeway R J, Russell C. T., Slavin J. A., et al.
Title: Global observations of magnetospheric high- m poloidal waves during the 22 June 2015 magnetic storm
Abstract: We report global observations of high-m poloidal waves during the recovery phase of the 22 June 2015 magnetic storm from a constellation of widely spaced satellites of five missions including Magnetospheric Multiscale (MMS), Van Allen Probes, Time History of Events and Macroscale Interactions during Substorm (THEMIS), Cluster, and Geostationary Operational Environmental Satellites (GOES). The combined observations demonstrate the global spatial extent of storm time poloidal waves. MMS observations confirm high azimuthal wave numbers (m ~ 100). Mode identification indicates the waves are associated with the second harmonic of field line resonances. The wave frequencies exhibit a decreasing trend as L increases, distinguishing them from the single-frequency global poloidal modes normally obs. . .
Date: 04/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073048 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL073048/full
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Authors: Claudepierre S G, O'Brien T P, Fennell J. F., Blake J B, Clemmons J. H., et al.
Title: The hidden dynamics of relativistic electrons (0.7-1.5 MeV) in the inner zone and slot region
Abstract: We present measurements of relativistic electrons (0.7–1.5 MeV) in the inner zone and slot region obtained by the Magnetic Electron and Ion Spectrometer (MagEIS) instrument on Van Allen Probes. The data presented are corrected for background contamination, which is primarily due to inner-belt protons in these low-L regions. We find that ∼1 MeV electrons were transported into the inner zone following the two largest geomagnetic storms of the Van Allen Probes era to date, the March and June 2015 events. As ∼1 MeV electrons were not observed in Van Allen Probes data in the inner zone prior to these two events, the injections created a new inner belt that persisted for at least 1.5 years. In contrast, we find that electrons injected into the slot region decay on much faster timescales, a. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023719 Available at: http://doi.wiley.com/10.1002/2016JA023719
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Authors: Claudepierre S G, O'Brien T P, Fennell J. F., Blake J B, Clemmons J. H., et al.
Title: The hidden dynamics of relativistic electrons (0.7-1.5 MeV) in the inner zone and slot region
Abstract: We present measurements of relativistic electrons (0.7–1.5 MeV) in the inner zone and slot region obtained by the Magnetic Electron and Ion Spectrometer (MagEIS) instrument on Van Allen Probes. The data presented are corrected for background contamination, which is primarily due to inner-belt protons in these low-L regions. We find that ∼1 MeV electrons were transported into the inner zone following the two largest geomagnetic storms of the Van Allen Probes era to date, the March and June 2015 events. As ∼1 MeV electrons were not observed in Van Allen Probes data in the inner zone prior to these two events, the injections created a new inner belt that persisted for at least 1.5 years. In contrast, we find that electrons injected into the slot region decay on much faster timescales, a. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023719 Available at: http://doi.wiley.com/10.1002/2016JA023719http://onlinelibrary.wiley.com/wol1/doi/10.1002/2016JA023719
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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: Hartley D. P., Kletzing C A, Kurth W S, Hospodarsky G B, Bounds S R, et al.
Title: An improved sheath impedance model for the Van Allen probes EFW instrument: Effects of the spin axis antenna
Abstract: A technique to quantitatively determine the sheath impedance of the Van Allen Probes Electric Field and Waves (EFW) instrument is presented. This is achieved, for whistler mode waves, through a comparison between the total electric field wave power spectra calculated from magnetic field observations and cold plasma theory, and the total electric field wave power measured by the EFW spherical double probes instrument. In a previous study, a simple density-dependent sheath impedance model was developed in order to account for the differences between the observed and calculated wave electric field. The current study builds on this previous work by investigating the remaining discrepancies, identifying their cause, and developing an improved sheath impedance correction. Analysis reveals that a. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023597 Available at: http://doi.wiley.com/10.1002/2016JA023597
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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: Zhang Yang, Shi Run, Ni Binbin, Gu Xudong, Zhang Xianguo, et al.
Title: Inferring electromagnetic ion cyclotron wave intensity from low altitude POES proton flux measurements: A detailed case study with conjugate Van Allen Probes observations
Abstract: N/A
Date: 03/2017 Publisher: Advances in Space Research Pages: 1568 - 1576 DOI: 10.1016/j.asr.2016.12.035 Available at: http://www.sciencedirect.com/science/article/pii/S0273117716307578
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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: Turner D L, O'Brien T. P., Fennell J F, Claudepierre S. G., Blake J. B., et al.
Title: Investigating the source of near-relativistic and relativistic electrons in Earth's inner radiation belt
Abstract: Using observations from NASA's Van Allen Probes, we study the role of sudden particle enhancements at low L shells (SPELLS) as a source of inner radiation belt electrons. SPELLS events are characterized by electron intensity enhancements of approximately an order of magnitude or more in less than 1 day at L < 3. During quiet and average geomagnetic conditions, the phase space density radial distributions for fixed first and second adiabatic invariants are peaked at 2 < L < 3 for electrons ranging in energy from ~50 keV to ~1 MeV, indicating that slow inward radial diffusion is not the dominant source of inner belt electrons under quiet/average conditions. During SPELLS events, the evolution of electron distributions reveals an enhancement of phase space density that can e. . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/1999JA900445 Available at: http://onlinelibrary.wiley.com/doi/10.1029/1999JA900445
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Authors: Ukhorskiy A Y, Sitnov M I, Merkin V. G., Gkioulidou M., and Mitchell D G
Title: Ion acceleration at dipolarization fronts in the inner magnetosphere
Abstract: During geomagnetic storms plasma pressure in the inner magnetosphere is controlled by energetic ions of tens to hundreds of keV. Plasma pressure is the source of global storm time currents, which control the distribution of magnetic field and couple the inner magnetosphere and the ionosphere. Recent analysis showed that the buildup of hot ion population in the inner magnetosphere largely occurs in the form of localized discrete injections associated with sharp dipolarizations of magnetic field, similar to dipolarization fronts in the magnetotail. Because of significant differences between the ambient magnetic field and the dipolarization front properties in the magnetotail and the inner magnetosphere, the physical mechanisms of ion acceleration at dipolarization fronts in these two regions. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023304 Available at: http://doi.wiley.com/10.1002/2016JA023304
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Authors: Min Kyungguk, Denton Richard E, Liu Kaijun, Gary Peter, and Spence Harlan E.
Title: Ion Bernstein instability as a possible source for oxygen ion cyclotron harmonic waves
Abstract: This paper demonstrates that an ion Bernstein instability can be a possible source for recently reported electromagnetic waves with frequencies at or near the singly ionized oxygen ion cyclotron frequency, inline image, and its harmonics. The particle measurements during strong wave activity revealed a relatively high concentration of oxygen ions (∼15%) whose phase space density exhibits a local peak at energy ∼20 keV. Given that the electron plasma-to-cyclotron frequency ratio is inline image, this energy corresponds to the particle speed inline image, where vA is the oxygen Alfvén speed. Using the observational key plasma parameters, a simplified ion velocity distribution is constructed, where the local peak in the oxygen ion velocity distribution is represented by an isotropic s. . .
Date: 05/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA023979 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA023979/full
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Authors: Tetrick S. S., Engebretson M. J., Posch J. L., Olson C. N., Smith C W, et al.
Title: Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations
Abstract: We have studied the spatial location relative to the plasmapause (PP) of the most intense electromagnetic ion cyclotron (EMIC) waves observed on Van Allen Probes A and B during their first full precession in local time. Most of these waves occurred over an L range of from -1 to +2 RE relative to the PP. Very few events occurred only within 0.1 RE of the PP, and events with a width in L of < 0.2 REoccurred both inside and outside the PP. Wave occurrence was always associated with high densities of ring current ions; plasma density gradients or enhancements were associated with some events but were not dominant factors in determining the sites of wave generation. Storm main and recovery phase events in the dusk sector were often inside the PP, and dayside events during quiet times and co. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023392 Available at: http://doi.wiley.com/10.1002/2016JA023392
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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: Khazanov G. V., Boardsen S., Krivorutsky E. N., Engebretson M. J., Sibeck D., et al.
Title: Lower hybrid frequency range waves generated by ion polarization drift due to electromagnetic ion cyclotron waves: Analysis of an event observed by the Van Allen Probe B
Abstract: We analyze a wave event that occurred near noon between 07:03 and 07:08 UT on 23 February 2014 detected by the Van Allen Probes B spacecraft, where waves in the lower hybrid frequency range (LHFR) and electromagnetic ion cyclotron (EMIC) waves are observed to be highly correlated, with Pearson correlation coefficient of ~0.86. We assume that the correlation is the result of LHFR wave generation by the ions' polarization drift in the electric field of the EMIC waves. To check this assumption the drift velocities of electrons and H+, He+, and O+ ions in the measured EMIC wave electric field were modeled. Then the LHFR wave linear instantaneous growth rates for plasma with these changing drift velocities and different plasma compositions were calculated. The time distribution of these growth . . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics Pages: 449 - 463 DOI: 10.1002/2016JA022814 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA022814/full
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Authors: Khazanov G. V., Boardsen S., Krivorutsky E. N., Engebretson M. J., Sibeck D., et al.
Title: Lower hybrid frequency range waves generated by ion polarization drift due to electromagnetic ion cyclotron waves: Analysis of an event observed by the Van Allen Probe B
Abstract: We analyze a wave event that occurred near noon between 07:03 and 07:08 UT on 23 February 2014 detected by the Van Allen Probes B spacecraft, where waves in the lower hybrid frequency range (LHFR) and electromagnetic ion cyclotron (EMIC) waves are observed to be highly correlated, with Pearson correlation coefficient of ~0.86. We assume that the correlation is the result of LHFR wave generation by the ions' polarization drift in the electric field of the EMIC waves. To check this assumption the drift velocities of electrons and H+, He+, and O+ ions in the measured EMIC wave electric field were modeled. Then the LHFR wave linear instantaneous growth rates for plasma with these changing drift velocities and different plasma compositions were calculated. The time distribution of these growth . . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022814 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA022814
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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: 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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