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2015
Authors: Yu Yiqun, Jordanova Vania, Zou Shasha, Heelis Roderick, Ruohoniemi Mike, et al.
Title: Modeling sub-auroral polarization streams (SAPS) during the March 17, 2013 storm
Abstract: The sub-auroral polarization streams (SAPS) are one of the most important features in representing magnetosphere-ionosphere coupling processes. In this study, we use a state-of-the-art modeling framework that couples an inner magnetospheric ring current model RAM-SCB with a global MHD model BATS-R-US and an ionospheric potential solver to study the SAPS that occurred during the March 17, 2013 storm event as well as to assess the modeling capability. Both ionospheric and magnetospheric signatures associated with SAPS are analyzed to understand the spatial and temporal evolution of the electrodynamics in the mid-latitude regions. Results show that the model captures the SAPS at sub-auroral latitudes, where Region-2 field-aligned currents (FACs) flow down to the ionosphere and the conductance. . .
Date: 02/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020371 Available at: http://doi.wiley.com/10.1002/2014JA020371
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Authors: Zhu Hui, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Plasmatrough exohiss waves observed by Van Allen Probes: Evidence for leakage from plasmasphere and resonant scattering of radiation belt electrons
Abstract: Exohiss waves are whistler mode hiss observed in the plasmatrough region. We present a case study of exohiss waves and the corresponding background plasma distributions observed by the Van Allen Probes in the dayside low-latitude region. The analysis of wave Poynting fluxes, suprathermal electron fluxes and cold electron densities supports the scenario that exohiss leaks from the plasmasphere into the plasmatrough. Quasilinear calculations further reveal that exohiss can potentially cause the resonant scattering loss of radiation belt electrons ~Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062964 Available at: http://doi.wiley.com/10.1002/2014GL062964
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Authors: Gkioulidou Matina, Ohtani S, Mitchell D G, Ukhorskiy A., Reeves G D, et al.
Title: Spatial structure and temporal evolution of energetic particle injections in the inner magnetosphere during the 14 July 2013 substorm event.
Abstract: Recent results by the Van Allen Probes mission showed that the occurrence of energetic ion injections inside geosynchronous orbit could be very frequent throughout the main phase of a geomagnetic storm. Understanding, therefore, the formation and evolution of energetic particle injections is critical in order to quantify their effect in the inner magnetosphere. We present a case study of a substorm event that occurred during a weak storm (Dst ~ - 40 nT) on 14 July 2013. Van Allen Probe B, inside geosynchronous orbit, observed two energetic proton injections within ten minutes, with different dipolarization signatures and duration. The first one is a dispersionless, short timescale injection pulse accompanied by a sharp dipolarization signature, while the second one is a dispersed, longer t. . .
Date: 02/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020872 Available at: http://doi.wiley.com/10.1002/2014JA020872
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Authors: O'Brien T.P., Claudepierre S.G., Looper M.D., Blake J.B., Fennell J.F., et al.
Title: On the use of drift echoes to characterize on-orbit sensor discrepancies
Abstract: We describe a method for using drift echo signatures in on-orbit data to resolve discrepancies between different measurements of particle flux. The drift period has a well-defined energy dependence, which gives rise to time dispersion of the echoes. The dispersion can then be used to determine the effective energy for one or more channels given each channel's drift period and the known energy for a reference channel. We demonstrate this technique on multiple instruments from the Van Allen probes mission. Drift echoes are only easily observed at high energies (100s keV to multiple MeV), where several drift periods occur before the observing satellite has moved on or the global magnetic conditions have changed. We describe a first-order correction for spacecraft motion. The drift echo techni. . .
Date: 02/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020859 Available at: http://doi.wiley.com/10.1002/2014JA020859
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Authors: Fennell J. F., Claudepierre S G, Blake J B, O'Brien T P, Clemmons J. H., et al.
Title: Van Allen Probes show the inner radiation zone contains no MeV electrons: ECT/MagEIS data
Abstract: We present Van Allen Probe observations of electrons in the inner radiation zone. The measurements were made by the ECT/MagEIS sensors that were designed to measure electrons with the ability to remove unwanted signals from penetrating protons, providing clean measurements. No electrons >900 keV were observed with equatorial fluxes above background (i.e. >0.1 electrons/(cm2 s sr keV)) in the inner zone. The observed fluxes are compared to the AE9 model and CRRES observations. Electron fluxes <200 keV exceeded the AE9 model 50% fluxes and were lower than the higher energy model fluxes. Phase space density radial profiles for 1.3≤L*<2.5 had mostly positive gradients except near L*~2.1 where the profiles for μ = 20-30 MeV/G were flat or slightly peaked. The major result is that MagEIS data. . .
Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062874 Available at: http://doi.wiley.com/10.1002/2014GL062874
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Authors: Kurth W S, De Pascuale S., Faden J. B., Kletzing C A, Hospodarsky G B, et al.
Title: Electron Densities Inferred from Plasma Wave Spectra Obtained by the Waves Instrument on Van Allen Probes
Abstract: The twin Van Allen Probe spacecraft, launched in August 2012, carry identical scientific payloads. The Electric and Magnetic Fields Instrument Suite and Integrated Science (EMFISIS) suite includes a plasma wave instrument (Waves) that measures three magnetic and three electric components of plasma waves in the frequency range of 10 Hz to 12 kHz using triaxial search coils and the Electric Fields and Waves (EFW) triaxial electric field sensors. The Waves instrument also measures a single electric field component of waves in the frequency range of 10 to 500 kHz. A primary objective of the higher frequency measurements is the determination of the electron density ne at the spacecraft, primarily inferred from the upper hybrid resonance frequency fuh. Considerable work has gone into developing . . .
Date: 01/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020857 Available at: http://doi.wiley.com/10.1002/2014JA020857
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Authors: Stephens G. K., Sitnov M I, Ukhorskiy A Y, Roelof E. C., Tsyganenko N A, et al.
Title: Empirical modeling of the storm-time innermost magnetosphere using Van Allen Probes and THEMIS data: Eastward and banana currents
Abstract: The structure of storm-time currents in the inner magnetosphere, including its innermost region inside 4RE, is studied for the first time using a modification of the empirical geomagnetic field model TS07D and new data from Van Allen Probes and THEMIS missions. It is shown that the model, which uses basis-function expansions instead of ad hoc current modules to approximate the magnetic field, consistently improves its resolution and magnetic field reconstruction with the increase of the number of basis functions and resolves the spatial structure and evolution of the innermost eastward current. This includes a connection between the westward ring current flowing largely at inline image and the eastward ring current concentrated at inline image resulting in a vortex current pattern. A simil. . .
Date: 01/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA021700 Available at: http://doi.wiley.com/10.1002/2015JA021700
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Authors: Foster J. C., Wygant J R, Hudson M K, Boyd A. J., Baker D N, et al.
Title: Shock-Induced Prompt Relativistic Electron Acceleration In the Inner Magnetosphere
Abstract: We present twin Van Allen Probes spacecraft observations of the effects of a solar wind shock impacting the magnetosphere on 8 October 2013. The event provides details both of the accelerating electric fields associated with the shock and the response of inner magnetosphere electron populations across a broad range of energies. During this period the two Van Allen Probes observed shock effects from the vantage point of the dayside magnetosphere at radial positions of L=3 and L=5, at the location where shock-induced acceleration of relativistic electrons occurs. The extended (~1 min) duration of the accelerating electric field across a broad extent of the dayside magnetosphere, coupled with energy dependent relativistic electron gradient drift velocities, selects a preferred range of energi. . .
Date: 01/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020642 Available at: http://doi.wiley.com/10.1002/2014JA020642
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Authors: Li X, Selesnick R. S., Baker D N, Jaynes A. N., Kanekal S G, et al.
Title: Upper limit on the inner radiation belt MeV electron Intensity
Abstract: No instruments in the inner radiation belt are immune from the unforgiving penetration of the highly energetic protons (10s of MeV to GeV). The inner belt proton flux level, however, is relatively stable, thus for any given instrument, the proton contamination often leads to a certain background noise. Measurements from the Relativistic Electron and Proton Telescope integrated little experiment (REPTile) on board Colorado Student Space Weather Experiment (CSSWE) CubeSat, in a low Earth orbit, clearly demonstrate that there exist sub-MeV electrons in the inner belt because of their flux level is orders of magnitude higher than the background, while higher energy electron (>1.6 MeV) measurements cannot be distinguished from the background. Detailed analysis of high-quality measurements from . . .
Date: 01/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020777 Available at: http://doi.wiley.com/10.1002/2014JA020777
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Authors: Korotova G. I., Sibeck D G, Tahakashi K., Dai L., Spence H E, et al.
Title: Van Allen Probe observations of drift-bounce resonances with Pc 4 pulsations and wave–particle interactions in the pre-midnight inner magnetosphere
Abstract: We present Van Allen Probe B observations of azimuthally limited, antisymmetric, poloidal Pc 4 electric and magnetic field pulsations in the pre-midnight sector of the magnetosphere from 05:40 to 06:00 UT on 1 May 2013. Oscillation periods were similar for the magnetic and electric fields and proton fluxes. The flux of energetic protons exhibited an energy-dependent response to the pulsations. Energetic proton variations were anticorrelated at medium and low energies. Although we attribute the pulsations to a drift-bounce resonance, we demonstrate that the energy-dependent response of the ion fluxes results from pulsation-associated velocities sweeping energy-dependent radial ion flux gradients back and forth past the spacecraft.
Date: 01/2015 Publisher: Annales Geophysicae Pages: 955 - 964 DOI: 10.5194/angeo-33-955-2015 Available at: http://www.ann-geophys.net/33/955/2015/angeo-33-955-2015.pdf
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2014
Authors: Jaynes A. N., Li X, Schiller Q. G., Blum L. W., Tu W., et al.
Title: Evolution of relativistic outer belt electrons during an extended quiescent period
Abstract: To effectively study steady loss due to hiss-driven precipitation of relativistic electrons in the outer radiation belt, it is useful to isolate this loss by studying a time of relatively quiet geomagnetic activity. We present a case of initial enhancement and slow, steady decay of 700 keV - 2 MeV electron populations in the outer radiation belt during an extended quiescent period from ~15 December 2012 - 13 January 2013. We incorporate particle measurements from a constellation of satellites, including the Colorado Student Space Weather Experiment (CSSWE) CubeSat, the Van Allen Probes twin spacecraft, and THEMIS, to understand the evolution of the electron populations across pitch angle and energy. Additional data from calculated phase space density (PSD), as well as hiss and chorus w. . .
Date: 12/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020125 Available at: http://doi.wiley.com/10.1002/2014JA020125
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Authors: Summers Danny, Omura Yoshiharu, Nakamura Satoko, and Kletzing Craig A.
Title: Fine structure of plasmaspheric hiss
Abstract: Plasmaspheric hiss has been widely regarded as a broadband, structureless, incoherent emission. In this study, by examining burst-mode vector waveform data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument on the Van Allen Probes mission, we show that plasmaspheric hiss is a coherent emission with complex fine structure. Specifically, plasmaspheric hiss appears as discrete rising tone and falling tone elements. Our study comprises the analysis of two one-hour samples within which a total of 8 one-second samples were analyzed. By means of waveform analysis on two samples we identify typical amplitudes, phase profiles, and sweep rates of the rising and falling tone elements. The exciting new observations reported here can be expected to fuel a . . .
Date: 12/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020437 Available at: http://doi.wiley.com/10.1002/2014JA020437
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Authors: Li Zan, Millan Robyn M., Hudson Mary K, Woodger Leslie A., Smith David M., et al.
Title: Investigation of EMIC wave scattering as the cause for the BARREL January 17, 2013 relativistic electron precipitation event: a quantitative comparison of simulation with observations
Abstract: Electromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the BARREL balloons, and was magnetically mapped close to GOES-13. We simulate the relativistic electron pitch-angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES-13 and the Van Allen Probes. We show that the count rate, the energy distribution and the time variation of the simulated precipitation all agree very well with the balloon observations, suggesting that EMIC wave scattering was likely the cause for the precipitation event. The event reported here is . . .
Date: 12/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062273 Available at: http://doi.wiley.com/10.1002/2014GL062273
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Authors: Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Quantifying the relative contributions of substorm injections and chorus waves to the rapid outward extension of electron radiation belt
Abstract: We study the rapid outward extension of the electron radiation belt on a timescale of several hours during three events observed by RBSP and THEMIS satellites, and particularly quantify the contributions of substorm injections and chorus waves to the electron flux enhancement near the outer boundary of radiation belt. A comprehensive analysis including both observations and simulations is performed for the first event on 26 May 2013. The outer boundary of electron radiation belt moved from L = 5.5 to L > 6.07 over about 6 hours, with up to four orders of magnitude enhancement in the 30 keV-5 MeV electron fluxes at L = 6. The observations show that the substorm injection can cause 100% and 20% of the total subrelativistic (~0.1 MeV) and relativistic (2-5 MeV) electron . . .
Date: 12/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020709 Available at: http://doi.wiley.com/10.1002/2014JA020709
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Authors: Betz Eric O.
Title: Trapping waves in Earth's plasmasphere
Abstract: Earth's magnetic field traps donut-shaped bands of radiation in a belt around the planet that react to solar eruptions by growing and shrinking. The Van Allen belts consist of two rings filled with particles from the solar wind and cosmic rays. Within the outer ring of the Van Allen belt sits the plasmasphere, which is the innermost part of the planet's magnetic field and home to low-energy charged particles.
Date: 12/2014 Publisher: Eos, Transactions American Geophysical Union Pages: 472 - 472 DOI: 10.1002/2014EO490016 Available at: http://doi.wiley.com/10.1002/eost.v95.49http://doi.wiley.com/10.1002/2014EO490016
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Authors: Boardsen S. A., Hospodarsky G B, Kletzing C A, Pfaff R. F., Kurth W S, et al.
Title: Van Allen Probe Observations of Periodic Rising Frequencies of the Fast Magnetosonic Mode
Abstract: Near simultaneous periodic dispersive features of fast magnetosonic mode emissions are observed by both Van Allen Probes spacecraft while separated in magnetic local time by ~5 hours: Probe A at 15 and Probe B at 9–11 hours. Both spacecraft see similar frequency features, characterized by a periodic repetition at ~180 s. Each repetition is characterized by a rising frequency. Since no modulation is observed in the proton shell distribution, the plasma density, or in the background magnetic field at either spacecraft we conclude that these waves are not generated near the spacecraft but external to both spacecraft locations. Probe A while outside the plasmapause sees the start of each repetition ~40 s before probe B while deep inside the plasmasphere. We can qualitatively reproduce . . .
Date: 12/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062020 Available at: http://doi.wiley.com/10.1002/2014GL062020
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Authors: Zhao H., Li X, Blake J B, Fennell J. F., Claudepierre S G, et al.
Title: Characteristics of pitch angle distributions of 100 s keV electrons in the slot region and inner radiation belt
Abstract: The pitch angle distribution (PAD) of energetic electrons in the slot region and inner radiation belt received little attention in the past decades due to the lack of quality measurements. Using the state-of-art pitch-angle-resolved data from the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard the Van Allen Probes, a detailed analysis of 100 s keV electron PADs below L = 4 is performed, in which the PADs is categorized into three types: normal (flux peaking at 90∘), cap (exceedingly peaking narrowly around 90∘) and 90∘-minimum (lower flux at 90∘) PADs. By examining the characteristics of the PADs of ~460 keV electrons for over a year, we find that the 90∘-minimum PADs are generally present in the inner belt (L < 2), while normal PADs dominate at .L ~3.5. . .
Date: 11/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020386 Available at: http://doi.wiley.com/10.1002/2014JA020386
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Authors: Mauk B H
Title: Comparative Investigation of the Energetic Ion Spectra Comprising the Magnetospheric Ring Currents of the Solar System
Abstract: Investigated here are factors that control the intensities and shapes of energetic ion spectra that make up the ring current populations of the strongly magnetized planets of the solar system, specifically those of Earth, Jupiter, Saturn, Uranus, and Neptune. Following a previous and similar comparative investigation of radiation belt electrons, we here turn our attention to ions. Specifically, we examine the possible role of the differential ion Kennel-Petschek limit, as moderated by Electromagnetic Ion Cyclotron (EMIC) waves, as a standard for comparing the most intense ion spectra within the strongly magnetized planetary magnetospheres. In carrying out this investigation, the substantial complexities engendered by the very different ion composition distributions of these diverse magneto. . .
Date: 11/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020392 Available at: http://doi.wiley.com/10.1002/2014JA020392
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Authors: Zhou Qinghua, Xiao Fuliang, Yang Chang, Liu Si, Kletzing C A, et al.
Title: Excitation of nightside magnetosonic waves observed by Van Allen Probes
Abstract: During the recovery phase of the geomagnetic storm on 30-31 March 2013, Van Allen Probe A detected enhanced magnetosonic (MS) waves in a broad range of L =1.8-4.7 and MLT =17-22 h, with a frequency range ~10-100 Hz. In the meanwhile, distinct proton ring distributions with peaks at energies of ~10 keV, were also observed in L =3.2-4.6 and L =5.0-5.6. Using a subtracted bi-Maxwellian distribution to model the observed proton ring distribution, we perform three dimensional ray tracing to investigate the instability, propagation and spatial distribution of MS waves. Numerical results show that nightside MS waves are produced by proton ring distribution and grow rapidly from the source location L =5.6 to the location L =5.0, but remain nearly stable at locations L <5.0 Moreover, waves launched. . .
Date: 11/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2014JA020481 Available at: http://doi.wiley.com/10.1002/2014JA020481
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Authors: Baker D N, Jaynes A. N., Hoxie V C, Thorne R M, Foster J. C., et al.
Title: An impenetrable barrier to ultrarelativistic electrons in the Van Allen radiation belts
Abstract: Early observations1, 2 indicated that the Earth’s Van Allen radiation belts could be separated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. Subsequent studies3, 4 showed that electrons of moderate energy (less than about one megaelectronvolt) often populate both zones, with a deep ‘slot’ region largely devoid of particles between them. There is a region of dense cold plasma around the Earth known as the plasmasphere, the outer boundary of which is called the plasmapause. The two-belt radiation structure was explained as arising from strong electron interactions with plasmaspheric hiss just inside the plasmapause boundary5, with the inner edge of the outer radiation zone corresponding to the minimum plasmapause location6. Re. . .
Date: 11/2014 Publisher: Nature Pages: 531 - 534 DOI: 10.1038/nature13956 Available at: http://www.nature.com/doifinder/10.1038/nature13956
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Authors: Gerrard Andrew, Lanzerotti Louis, Gkioulidou Matina, Mitchell Donald, Manweiler Jerry, et al.
Title: Initial Measurements of O-ion and He-ion Decay Rates Observed from the Van Allen Probes RBSPICE Instrument
Abstract: H-ion (~45-keV to ~600-keV), He-ion (~65-keV to ~520-keV), and O-ion (~140-keV to ~1130-keV) integral flux measurements, from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft B, are reported. These abundance data form a cohesive picture of ring current ions during the first nine months of measurements. Furthermore, the data presented herein are used to show injection characteristics via the He-ion/H-ion abundance ratio and the O-ion/H-ion abundance ratio. Of unique interest to ring current dynamics are the spatial-temporal decay characteristics of the two injected populations. We observe that He-ions decay more quickly at lower L-shells, on the orderof ~0.8-day at L-shells of 3–4, and decay more slowly with higher L-she. . .
Date: 11/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020374 Available at: http://doi.wiley.com/10.1002/2014JA020374
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Authors: Zanetti L. J., Mauk B H, Fox N.J., Barnes R.J., Weiss M, et al.
Title: The Evolving Space Weather System - Van Allen Probes Contribution
Abstract: The overarching goal and purpose of the study of space weather is clear - to understand and address the issues caused by solar disturbances on humans and technological systems. Space weather has evolved in the past few decades from a collection of concerned agencies and researchers to a critical function of the National Weather Service of NOAA. The general effects have also evolved from the well-known telegraph disruptions of the mid-1800’s to modern day disturbances of the electric power grid, communications and navigation, human spaceflight and spacecraft systems. The last two items in this list, and specifically the effects of penetrating radiation, were the impetus for the space weather broadcast implemented on NASA’s Van Allen Probes’ twin pair of satellites, launched in August . . .
Date: 10/2014 Publisher: Space Weather DOI: 10.1002/2014SW001108 Available at: http://doi.wiley.com/10.1002/2014SW001108
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Authors: Hao Y. X., Zong Q.-G., Wang Y. F., Zhou X.-Z., Zhang Hui, et al.
Title: Interactions of energetic electrons with ULF waves triggered by interplanetary shock: Van Allen Probes observations in the magnetotail
Abstract: We present in situ observations of a shock-induced substorm-like event on 13 April 2013 observed by the newly launched Van Allen twin probes. Substorm-like electron injections with energy of 30–500 keV were observed in the region from L∼5.2 to 5.5 immediately after the shock arrival (followed by energetic electron drift echoes). Meanwhile, the electron flux was clearly and strongly varying on the ULF wave time scale. It is found that both toroidal and poloidal mode ULF waves with a period of 150 s emerged following the magnetotail magnetic field reconfiguration after the interplanetary (IP) shock passage. The poloidal mode is more intense than the toroidal mode. The 90° phase shift between the poloidal mode Br and Ea suggests the standing poloidal waves in the Northern Hemisphere. F. . .
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020023 Available at: http://doi.wiley.com/10.1002/2014JA020023
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Authors: Li Zhao, Hudson Mary, Jaynes Allison, Boyd Alexander, Malaspina David, et al.
Title: Modeling Gradual Diffusion Changes in Radiation Belt Electron Phase Space Density for the March 2013 Van Allen Probes Case Study
Abstract: March 2013 provided the first equinoctial period when all of the instruments on the Van Allen Probes spacecraft were fully operational. This interval was characterized by disturbances of outer zone electrons with two timescales of variation, diffusive and rapid dropout and restoration [Baker et al., 2014]. A radial diffusion model was applied to the month-long interval to confirm that electron phase space density is well described by radial diffusion for the whole month at low first invariant ≤400 MeV/G, but peaks in phase space density observed by the ECT instrument suite at higher first invariant are not reproduced by radial transport from a source at higher L. The model does well for much of the month-long interval, capturing three of four enhancements in phase space density which e. . .
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020359 Available at: http://doi.wiley.com/10.1002/2014JA020359
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Authors: Fu Xiangrong, Cowee Misa M., Friedel Reinhard H., Funsten Herbert O, Gary Peter, et al.
Title: Whistler Anisotropy Instabilities as the Source of Banded Chorus: Van Allen Probes Observations and Particle-in-Cell Simulations
Abstract: Magnetospheric banded chorus is enhanced whistler waves with frequencies ωr < Ωe, where Ωe is the electron cyclotron frequency, and a characteristic spectral gap at ωr ≃ Ωe/2. This paper uses spacecraft observations and two-dimensional particle-in-cell (PIC) simulations in a magnetized, homogeneous, collisionless plasma to test the hypothesis that banded chorus is due to local linear growth of two branches of the whistler anisotropy instability excited by two distinct, anisotropic electron components of significantly different temperatures. The electron densities and temperatures are derived from HOPE instrument measurements on the Van Allen Probes A satellite during a banded chorus event on 1 November 2012. The observations are consistent with a three-component electron mod. . .
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020364 Available at: http://doi.wiley.com/10.1002/2014JA020364
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Authors: Fok M.-C., Buzulukova N. Y., Chen S.-H., Glocer A., Nagai T., et al.
Title: The Comprehensive Inner Magnetosphere-Ionosphere Model
Abstract: Simulation studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the r. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7522 - 7540 DOI: 10.1002/jgra.v119.910.1002/2014JA020239 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA020239
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Authors: Wang X., Malaspina D. M., Hsu H.-W., Ergun R. E., and M. Horányi.
Title: The effects of magnetic fields on photoelectron-mediated spacecraft potential fluctuations
Abstract: Previously, we have experimentally studied photoelectron-mediated spacecraft potential fluctuations associated with time-dependent external electric fields. In this paper, we investigate the effects of magnetic fields on such spacecraft potential fluctuations. A magnetic field is created above the UV-illuminated surface of a spacecraft model to alter the escape rate of photoelectrons. The packet of the observed potential oscillations becomes less positive with increasing magnetic field strength because more of the emitted photoelectrons are returned to the surface. As a result, the photoelectric charging time is increased, corresponding to a decrease in the response frequency of the photoemitting surface. The amplitude of the potential oscillations decreases when the response frequency bec. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7319 - 7326 DOI: 10.1002/jgra.v119.910.1002/2014JA019923 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA019923
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Authors: Baker Daniel
Title: New Twists in Earth’s Radiation Belts
Abstract: In 1958, an early satellite, Explorer I, made the discovery that Earth is enshrouded in belts of extraordinarily high-energy, high-intensity radiation. Now called the Van Allen belts, after the researcher who led that satellite mission, these rings are known to wax and wane in intensity, for reasons that are still being investigated. Satellites now criss-cross these belts, so understanding what influences them has dire implications for communications and other technologies in our modern age. Solar storms and space weather can pump them up, making the radiation zones around Earth immensely more dangerous for days or even weeks on end. The author has been involved with instruments on the dual Radiation Belt Storm Probes satellites that were launched on August 30, 2012, into Earth orbit to st. . .
Date: 09/2014 Publisher: American Scientist Pages: 374 DOI: 10.1511/2014.110.374 Available at: http://www.americanscientist.org/issues/feature/2014/5/new-twists-in-earths-radiation-belts
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Authors: Gkioulidou Matina, Ukhorskiy A., Mitchell D G, Sotirelis T., Mauk B., et al.
Title: The role of small-scale ion injections in the buildup of Earth's ring current pressure: Van Allen Probes observations of the March 17 th , 2013 storm
Abstract: Energetic particle transport into the inner magnetosphere during geomagnetic storms is responsible for significant plasma pressure enhancement, which is the driver of large-scale currents that control the global electrodynamics within the magnetosphere-ionosphere system. Therefore, understanding the transport of plasma from the tail deep into the near-Earth magnetosphere, as well as the energization processes associated with this transport, is essential for a comprehensive knowledge of the near-Earth space environment. During the main phase of a geomagnetic storm on March 17th 2013 (minimum Dst ~ −137 nT), the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on the Van Allen Probes observed frequent, small-scale proton injections deep into the inner nightsi. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020096 Available at: http://doi.wiley.com/10.1002/2014JA020096
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Authors: Goldstein J, De Pascuale S., Kletzing C., Kurth W., Genestreti K. J., et al.
Title: Simulation of Van Allen Probes Plasmapause Encounters
Abstract: We use an E × B-driven plasmapause test particle (PTP) simulation to provide global contextual information for in situ measurements by the Van Allen Probes (RBSP) during 15–20 January 2013. During 120 h of simulation time beginning on 15 January, geomagnetic activity produced three plumes. The third and largest simulated plume formed during enhanced convection on 17 January, and survived as a rotating, wrapped, residual plume for tens of hours. To validate the simulation, we compare its output with RBSP data. Virtual RBSP satellites recorded 28 virtual plasmapause encounters during 15–19 January. For 26 of 28 (92%) virtual crossings, there were corresponding actual RBSP encounters with plasmapause density gradients. The mean difference in encounter time between model and data is. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020252 Available at: http://doi.wiley.com/10.1002/2014JA020252
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Authors: Ma Q, Li W, Chen L, Thorne R M, Kletzing C A, et al.
Title: The trapping of equatorial magnetosonic waves in the Earth's outer plasmasphere
Abstract: We investigate the excitation and propagation of equatorial magnetosonic waves observed by the Van Allen Probes and describe evidence for a trapping mechanism for magnetosonic waves in the Earth's plasmasphere. Intense equatorial magnetosonic waves were observed inside the plasmasphere in association with a pronounced proton ring distribution, which provides free energy for wave excitation. Instability analysis along the inbound orbit demonstrates that broadband magnetosonic waves can be excited over a localized spatial region near the plasmapause. The waves can subsequently propagate into the inner plasmasphere and remain trapped over a limited radial extent, consistent with the predictions of near-perpendicular propagation. By performing a similar analysis on another observed magnetosoni. . .
Date: 09/2014 Publisher: Geophysical Research Letters Pages: 6307 - 6313 DOI: 10.1002/2014GL061414 Available at: http://doi.wiley.com/10.1002/2014GL061414
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Authors: Reeves G D, Spence H E, Henderson M G, Tu W., Cunningham G. S., et al.
Title: Acceleration and loss driven by VLF chorus: Van Allen Probes observations and DREAM model results
Abstract: For over a decade now we have understood the response of the Earth's radiation belts to solar wind driving are a delicate balance of acceleration and loss processes. Theory has shown that the interaction of relativistic electrons with VLF whistler mode chorus can produce both energization through momentum diffusion and loss through pitch angle diffusion. Recent results from the Van Allen Probes mission has confirmed observationally that chorus can produce both acceleration and loss. The Van Allen Probes satellites are able to measure all the critical particle populations and wave fields with unprecedented precision and resolution but only at the two spacecraft locations. Those spatially-localized observations can be extended globally using three-dimensional diffusion codes such as the DREA. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929879 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929879
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Authors: Li W, Ni B, Thorne R M, Bortnik J, Green J C, et al.
Title: Calculation of whistler-mode wave intensity using energetic electron precipitation
Abstract: The energetic electron population measured by multiple low-altitude POES satellites is used to infer whistlermode wave amplitudes using a physics-based inversion technique. We validate this technique by quantitatively analyzing a conjunction event between the Van Allen Probes and POES, and find that the inferred hiss wave amplitudes from POES electron measurements agree remarkably well with directly measured hiss waves amplitudes. We also use this technique to construct the global distribution of chorus wave intensity with extensive coverage over a broad L-MLT region during the 8–9 October 2012 storm and demonstrate that the inferred chorus wave amplitudes agree well with conjugate measurements of chorus wave amplitudes from the Van Allen Probes. The evolution of the whistler-mode wave i. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929965 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929965
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Authors: Su Zhenpeng, Xiao Fuliang, Zheng Huinan, and Zhu Hui
Title: Chorus-driven acceleration of radiation belt electrons in the unusual temporal/spatial regions
Abstract: Cyclotron resonance with whistler-mode chorus waves is an important mechanism for the local acceleration of radiation belt energetic electrons. Such acceleration process has been widely investigated during the storm times, and its favored region is usually considered to be the low-density plasmatrough with magnetic local time (MLT) from midnight through dawn to noon. Here we present two case studies on the chorus-driven acceleration of radiation belt electrons in some “unusual” temporal /spatial regions. (1) The first event recorded by the Van Allen Probes during the nonstorm times from 21 to 23 February 2013. Within two days, a new radiation belt centering around L=5.8 formed and gradually merged with the original outer belt. The corresponding relativistic electron fluxes increased by. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929875 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929875
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Authors: Lui A. T. Y., Mitchell D G, and Lanzerotti L J
Title: Comparison of Energetic Electron Intensities Outside and Inside the Radiation Belts
Abstract: The intensities of energetic electrons (~25 – 800 keV) outside and inside Earth's radiation belts are reported using measurements from THEMIS and Van Allen Probes during non-geomagnetic storm periods. Three intervals of current disruption/dipolarization events in August, 2013 were selected for comparison. The following results are obtained. (1) Phase space densities (PSDs) for the equatorially mirroring electron population at three values of the first adiabatic invariant (20, 70, and 200 MeV/G) at the outer radiation belt boundary are found to be one to three orders of magnitude higher than values measured just inside the radiation belt. (2) There is indication that substorm activity leads to PSD increases inside L = 5.5 in less than 1 hr. (3) Evidence for progressive inward tr. . .
Date: 08/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020049 Available at: http://doi.wiley.com/10.1002/2014JA020049
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Authors: Thomas Evan G., Yan Jingye, Zhang Jiaojiao, Baker Joseph B. H., Ruohoniemi Michael, et al.
Title: An examination of the source of decameter-scale irregularities in the geomagnetically disturbed mid-latitude ionosphere
Abstract: We present first results from a study of the plasma instability mechanism responsible for the small-scale (∼10 m) ionospheric density irregularities commonly observed by the Super Dual Auroral Radar Network (SuperDARN) HF radars in the vicinity of Sub Auroral Polarization Streams (SAPS) during periods of geomagnetic disturbance. A focus is placed on the mid-latitude region of the ionosphere over North America where recent expansion of the SuperDARN network allows for extensive direct comparisons with total electron content (TEC) measurements from a dense network of ground-based GPS receivers. The TEC observations indicate that high-speed SAPS channels and the associated small-scale irregularities are typically located within the mid-latitude ionospheric trough. The Millstone Hill Incoher. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929853 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929853
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Authors: Chen Lunjin, Thorne Richard M, Bortnik Jacob, Li Wen, Horne Richard B, et al.
Title: Generation of Unusually Low Frequency Plasmaspheric Hiss
Abstract: It has been reported from Van Allen Probe observations that plasmaspheric hiss intensification in the outer plasmasphere, associated with a substorm injection on Sept 30 2012, occurred with a peak frequency near 100 Hz, well below the typical plasmaspheric hiss frequency range, extending down to ~20 Hz. We examine this event of unusually low frequency plasmaspheric hiss to understand its generation mechanism. Quantitative analysis is performed by simulating wave ray paths via the HOTRAY ray tracing code with measured plasma density and calculating ray path-integrated wave gain evaluated using the measured energetic electron distribution. We demonstrate that the growth rate due to substorm injected electrons is positive but rather weak, leading to small wave gain (~10 dB) during a sin. . .
Date: 08/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL060628 Available at: http://doi.wiley.com/10.1002/2014GL060628
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Authors: Foster J C
Title: Imaging the plasmasphere with ground based GPS TEC observations and comparisons with in situ plasmaspheric observations with Van Allen Probes
Abstract: For over a decade, incoherent scatter radar observations of the mid and auroral-latitude ionosphere combined with ground based GPS observations of total electron content (TEC) have been used to study the intense storm enhanced density (SED) plumes that form over the Americas during major geomagnetic storms [1]. Magnetic field mapping of the ionospheric observations to magnetospheric heights revealed close correspondence between the SED and plasmasphere erosion plumes observed from space in EUV imagery by the IMAGE satellite [2]. During the current solar cycle the global distribution of GPS receivers used in creating the TEC maps and movies has increased significantly providing near-continuous two-dimensional coverage of TEC morphology and dynamics over much the northern hemisphere mid and . . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929943 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929943
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Authors: Foster John C, and Erickson Philip J.
Title: Initial observations of plasma waves in the sub-auroral polarization stream with the Van Allen Probes
Abstract: The Sub-Auroral Polarization Stream (SAPS) is a geospace boundary layer phenomenon associated with the interaction of the warm plasma of the magnetospheric ring current with the cold ions and electrons of the outer plasmasphere [1]. Driven by ring current enhancements during magnetospheric disturbances, SAPS location, intensity, and characteristics are greatly influenced by the underlying ionosphere. Strong M-I coupling by means of field-aligned currents creates a high-speed (>1000 m/s) westward plasma flow channel in the ionosphere at pre-midnight/post-noon local times which is readily observable by incoherent scatter [2] and HF radars and in plasma drift observations by low-altitude spacecraft (e.g. DMSP). The fast ionospheric flows generate E-region irregularities providing for addition. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929852 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929852
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Authors: Malaspina D. M., Andersson L., Ergun R. E., Wygant J R, Bonnell J W, et al.
Title: Nonlinear Electric Field Structures in the Inner Magnetosphere
Abstract: Van Allen Probes observations are presented which demonstrate the presence of nonlinear electric field structures in the inner terrestrial magnetosphere (< 6 RE). A range of structures are observed, including phase space holes and double layers.These structures are observed over several Earth radii in radial distance and over a wide range of magnetic local times. They are observed in the dusk, midnight, and dawn sectors, with the highest concentration pre-midnight. Some nonlinear electric field structures are observed to coincide with dipolarizations of the magnetic field and increases in electron energy flux for energies between 1 keV and 30 keV. Nonlinear electric field structures possess isolated impulsive electric fields, often with a significant component parallel to the ambient m. . .
Date: 08/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL061109 Available at: http://doi.wiley.com/10.1002/2014GL061109
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Authors: Selesnick R. S., Baker D N, Jaynes A. N., Li X, Kanekal S G, et al.
Title: Observations of the inner radiation belt: CRAND and trapped solar protons
Abstract: Measurements of inner radiation belt protons have been made by the Van Allen Probes Relativistic Electron-Proton Telescopes as a function of kinetic energy (24 to 76 MeV), equatorial pitch angle, and magnetic L shell, during late-2013 and early-2014. A probabilistic data analysis method reduces background from contamination by higher energy protons. Resulting proton intensities are compared to predictions of a theoretical radiation belt model. Then trapped protons originating both from cosmic ray albedo neutron decay (CRAND) and from trapping of solar protons are evident in the measured distributions. An observed double-peaked distribution in L is attributed, based on the model comparison, to a gap in the occurrence of solar proton events during the 2007 to 2011 solar minimum. Equatorial. . .
Date: 08/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020188 Available at: http://doi.wiley.com/10.1002/2014JA020188
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Authors: Kletzing Craig A.
Title: Progress on understanding chorus emissions from data of the electric and magnetic field instrument suite and integrated science (EMFISIS) on the Van Allen Probes
Abstract: The physics of the creation, loss, and transport of radiation belt particles is intimately connected to the electric and magnetic fields which mediate these processes. A key wave-particle interaction important to both acceleration and loss in the radiation belts is the of whistler-mode chorus interacting with energetic electrons. To measure this important radiation belt interaction, the two-satellite Van Allen Probes mission utilizes one of the most complete sets of measurements ever made in the inner magnetosphere. As part of the mission, the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) investigation is an integrated set of instruments consisting of a tri-axial fluxgate magnetometer (MAG) and a Waves instrument which includes a tri-axial search coil magnet. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929872 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929872
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Authors: Foster John C, and Erickson Philip J.
Title: Prompt energization of relativistic and highly relativistic electrons during a substorm interval
Abstract: On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ∼6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons [1]. A 50% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. Chorus is excited following the injection of low-energy (1–30 keV) plasma sheet electrons into the inner magnetosphere [2]. During the 17 March substorm injection, cold plasma that had circulated into the nightside. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929876 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929876
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Authors: Thorne R M, Li W, Ma Q, Ni B, and Bortnik J
Title: Radiation belt electron acceleration by chorus waves during the 17 March 2013 storm
Abstract: Local acceleration driven by whistler-mode chorus waves is suggested to be fundamentally important for accelerating seed electron population to ultra-relativistic energies in the outer radiation belt. In this study, we quantitatively evaluate chorus-driven electron acceleration during the 17 March 2013 storm, when Van Allen Probes observed very rapid electron acceleration up to multi MeV within ∼15 hours. A clear peak in electron phase space density observed at L∗ ∼ 4 indicates that the internal local acceleration process was operating. We construct the global distribution of chorus wave intensity from the low-altitude electron measurements by multiple POES satellites over a broad L-MLT region, which is used to simulate the radiation belt electron dynamics driven by chorus waves. Our. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929882 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929882
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Authors: McCarthy Michael P., Millan Robyn M., Sample John G., and Smith David M.
Title: Radiation belt losses observed from multiple stratospheric balloons over Antarctica
Abstract: Relativistic electrons, trapped by Earth's magnetic field, have received increasing attention since increasing numbers of commercial and research spacecraft traverse regions of high radiation flux. The Van Allen probes were launched into Earth's radiation belts in September 2012, making comprehensive measurements of charged particle fluxes and electromagnetic fields, with the objective of a better understanding of the processes that modulate radiation belt fluxes. Because losses of radiation belt electrons to Earth's atmosphere are very difficult to measure from high altitude spacecraft, a balloon-based program, consisting of campaigns in January 2013 and 2014, was funded to measure losses in conjunction with the Van Allen probes mission. We present results from both balloon campaigns, whi. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929960 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929960
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Authors: Santolik O, Hospodarsky G B, Kurth W S, Averkamp T. F., Kletzing C A, et al.
Title: Statistical properties of wave vector directions of whistler-mode waves in the radiation belts based on measurements of the Van Allen probes and Cluster missions
Abstract: Wave-particle interactions in the Earth's Van Allen radiation belts are known to be an efficient process of the exchange of energy between different particle populations, including the energetic radiation belt particles. The whistler mode waves, especially chorus, can control the radiation belt dynamics via linear or nonlinear interactions with both the energetic radiation belt electrons and lower energy electron populations. Wave vector directions are a very important parameter of these wave-particle interactions. We use measurements of whistlermode waves by the WAVES instrument from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard the Van Allen Probes spacecraft covering the equatorial region of the Earth's magnetosphere in all MLT sectors, and a . . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929880 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929880
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Authors: Makela Jonathan J., Harding Brian J., Meriwether John W., Mesquita Rafael, Sanders Samuel, et al.
Title: Storm time response of the mid-latitude thermosphere: Observations from a network of Fabry-Perot interferometers
Abstract: Observations of thermospheric neutral winds and temperatures obtained during a geomagnetic storm on 2 October 2013 from a network of six Fabry-Perot interferometers (FPIs) deployed in the midwest United States are presented. Coincident with the commencement of the storm, the apparent horizontal wind is observed to surge westward and southward (towards the equator). Simultaneous to this surge in the apparent horizontal winds, an apparent downward wind of approximately 100 m/s lasting for 6 hours is observed. The apparent neutral temperature is observed to increase by approximately 400 K over all of the sites. Observations from an all-sky imaging system operated at the Millstone Hill observatory indicate the presence of a stable auroral red (SAR) arc and diffuse red aurora during this . . .
Date: 08/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA019832 Available at: http://doi.wiley.com/10.1002/2014JA019832
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Authors: Artemyev A. V., Agapitov O. V., Mozer F, and Krasnoselskikh V.
Title: Thermal electron acceleration by localized bursts of electric field in the radiation belts
Abstract: In this paper we investigate the resonant interaction of thermal ~10−100 eV electrons with a burst of electrostatic field that results in electron acceleration to kilovolt energies. This single burst contains a large parallel electric field of one sign and a much smaller, longer lasting parallel field of the opposite sign. The Van Allen Probe spacecraft often observes clusters of spatially localized bursts in the Earth's outer radiation belts. These structures propagate mostly away from thegeomagnetic equator and share properties of soliton-like nonlinear electron-acoustic waves: a velocity of propagation is about the thermal velocity of cold electrons (~3000−10000 km/s), and a spatial scale of electric field localization alongthe field lines is about the Debye radius of hot electrons . . .
Date: 08/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL061248 Available at: http://doi.wiley.com/10.1002/2014GL061248
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Authors: Schultz Colin
Title: Boom and bust for radiation belt high-energy electron populations
Abstract: Launched on 30 August 2012, the twin Van Allen probes constitute the first dedicated mission in decades to study the Earth's radiation belts. The sensor-laden spacecraft follow a nearly equatorial orbit, which gives them a complete view of the full range of radiation belt processes. In a new study, Baker et al. lay out some of the surprising results unveiled by the crafts' first year in orbit.
Date: 07/2014 Publisher: Eos, Transactions American Geophysical Union Pages: 260 - 260 DOI: 10.1002/eost.v95.2810.1002/2014EO280021 Available at: http://doi.wiley.com/10.1002/2014EO280021
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Authors: Mozer S., Agapitov O., Krasnoselskikh V., Lejosne S., Reeves D., et al.
Title: Direct Observation of Radiation-Belt Electron Acceleration from Electron-Volt Energies to Megavolts by Nonlinear Whistlers
Abstract: The mechanisms for accelerating electrons from thermal to relativistic energies in the terrestrial magnetosphere, on the sun, and in many astrophysical environments have never been verified. We present the first direct observation of two processes that, in a chain, cause this acceleration in Earth’s outer radiation belt. The two processes are parallel acceleration from electron-volt to kilovolt energies by parallel electric fields in time-domain structures (TDS), after which the parallel electron velocity becomes sufficiently large for Doppler-shifted upper band whistler frequencies to be in resonance with the electron gyration frequency, even though the electron energies are kilovolts and not hundreds of kilovolts. The electrons are then accelerated by the whistler perpendicular electri. . .
Date: 07/2014 Publisher: Physical Review Letters DOI: 10.1103/PhysRevLett.113.035001 Available at: http://link.aps.org/doi/10.1103/PhysRevLett.113.035001
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