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2016
Authors: Ripoll J. F., Reeves G., Cunningham G., Loridan V., Denton M., et al.
Title: Reproducing the observed energy-dependent structure of Earth's electron radiation belts during storm recovery with an event-specific diffusion model
Abstract: We present dynamic simulations of energy-dependent losses in the radiation belt " slot region" and the formation of the two-belt structure for the quiet days after the March 1st storm. The simulations combine radial diffusion with a realistic scattering model, based data-driven spatially and temporally-resolved whistler mode hiss wave observations from the Van Allen Probes satellites. The simulations reproduce Van Allen Probes observations for all energies and L-shells (2 to 6) including (a) the strong energy-dependence to the radiation belt dynamics (b) an energy-dependent outer boundary to the inner zone that extends to higher L-shells at lower energies and (c) an " S-shaped" energy-dependent inner boundary to the outer zone that results from the competition between diffusive radial tran. . .
Date: 05/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL068869 Available at: http://doi.wiley.com/10.1002/2016GL068869
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Authors: Ma Q, Li W, Thorne R M, Nishimura Y., Zhang X.-J., et al.
Title: Simulation of energy-dependent electron diffusion processes in the Earth's outer radiation belt
Abstract: The radial and local diffusion processes induced by various plasma waves govern the highly energetic electron dynamics in the Earth's radiation belts, causing distinct characteristics in electron distributions at various energies. In this study, we present our simulation results of the energetic electron evolution during a geomagnetic storm using the University of California, Los Angeles 3-D diffusion code. Following the plasma sheet electron injections, the electrons at different energy bands detected by the Magnetic Electron Ion Spectrometer (MagEIS) and Relativistic Electron Proton Telescope (REPT) instruments on board the Van Allen Probes exhibit a rapid enhancement followed by a slow diffusive movement in differential energy fluxes, and the radial extent to which electrons can penetra. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022507 Available at: http://doi.wiley.com/10.1002/2016JA022507
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Authors: Shi Run, Summers Danny, Ni Binbin, Manweiler Jerry W., Mitchell Donald G., et al.
Title: A statistical study of proton pitch angle distributions measured by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE)
Abstract: A statistical study of ring current-energy proton pitch angle distributions (PADs) in Earth's inner magnetosphere is reported here. The data are from the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on board the Van Allen Probe B spacecraft from January 1, 2013 to April 15, 2015. By fitting the data to the functional form sinnα, where α is the proton pitch angle, we examine proton PADs at the energies 50, 100, 180, 328 and 488 keV in the L-shell range from L = 2.5 to L = 6. Three PAD types are classified: trapped (90° peaked), butterfly and isotropic. The proton PAD dependence on the particle energy, MLT, L-shell, and geomagnetic activity are analyzed in detail. The results show a strong dependence of the proton PADs on MLT. On the nightside, the n values o. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA022140 Available at: http://doi.wiley.com/10.1002/2015JA022140
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Authors: Gkioulidou Matina, Ukhorskiy A., Mitchell D G, and Lanzerotti L J
Title: Storm-time dynamics of ring current protons: Implications for the long-term energy budget in the inner magnetosphere
Abstract: Our investigation of the long-term ring current proton pressure evolution in Earth's inner magnetosphere based on Van Allen Probes data shows drastically different behavior of the low- and high- energy components of the ring current proton population with respect to theSYM-H index variation. We found that while the low-energy component of the protons (<80 keV) is strongly governed by convective timescales and is very well correlated with the absolute value of SYM-H index, the high-energy component (>100 keV) varies on much longer timescales and shows either no correlation or anticorrelation with the absolute value of SYM-H index. Our study also shows that the contributions of the low- and high- energy protons to the inner magnetosphere energy content are comparable. Thus, our results c. . .
Date: 05/2016 Publisher: Geophysical Research Letters Pages: n/a - n/a DOI: 10.1002/2016GL068013 Available at: http://doi.wiley.com/10.1002/2016GL068013
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Authors: Liu Y., Zong Q.-G., Zhou X.-Z., Foster J. C., and Rankin R
Title: Structure and Evolution of Electron "Zebra Stripes" in the Inner Radiation Belt
Abstract: Zebra stripes” are newly found energetic electron energy-spatial (L shell) distributed structure with an energy between tens to a few hundreds keV in the inner radiation belt. Using high-quality measurements of electron fluxes from Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on board the twin Van Allen Probes, we carry out case and statistical studies from April 2013 to April 2014 to study the structural and evolutionary characteristics of zebra stripes below L = 3. It is revealed that the zebra stripes can be transformed into evenly spaced patterns in the electron drift frequency coordinate: the detrended logarithmic fluxes in each L shell region can be well described by sinusoidal functions of drift frequency. The “wave number” of this sinusoidal function, whic. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA022077 Available at: http://doi.wiley.com/10.1002/2015JA022077
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Authors: Kessel Mona
Title: Things we don't yet understand about solar driving of the radiation belts.
Abstract: This commentary explores how close we are to predicting the behavior of the radiations belts - the primary science objective of NASA's Van Allen Probes mission. Starting with what we know or think we know about competing sources, enhancement, transport, and loss, I walk through recent papers that have improved our understanding and then focus on flux dropouts as one particular yardstick of success. I mention a new paradigm for electrons and the importance of reliably matching models and observations for different solar inputs. Although the case for prediction remains a work in progress, there are encouraging signs of progress.
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022472 Available at: http://doi.wiley.com/10.1002/2016JA022472
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Authors: Hartley D. P., Kletzing C A, Kurth W S, Bounds S R, Averkamp T. F., et al.
Title: Using the cold plasma dispersion relation and whistler-mode waves to quantify the antenna sheath impedance of the Van Allen Probes EFW instrument
Abstract: Cold plasma theory and parallel wave propagation are often assumed when approximating the whistler mode magnetic field wave power from electric field observations. The current study is the first to include the wave normal angle from the Electric and Magnetic Field Instrument Suite and Integrated Science package on board the Van Allen Probes in the conversion factor, thus allowing for the accuracy of these assumptions to be quantified. Results indicate that removing the assumption of parallel propagation does not significantly affect calculated plasmaspheric hiss wave powers. Hence, the assumption of parallel propagation is valid. For chorus waves, inclusion of the wave normal angle in the conversion factor leads to significant alterations in the distribution of wave power ratios (observed/. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022501 Available at: http://doi.wiley.com/10.1002/2016JA022501
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Authors: Halford A J, McGregor S. L., Hudson M K, Millan R M, and Kress B T
Title: BARREL observations of a Solar Energetic Electron and Solar Energetic Proton event
Abstract: During the second Balloon Array for Radiation Belt Relativistic Electron Losses (BARREL) campaign two solar energetic proton (SEP) events were observed. Although BARREL was designed to observe X-rays created during electron precipitation events, it is sensitive to X-rays from other sources. The gamma lines produced when energetic protons hit the upper atmosphere are used in this paper to study SEP events. During the second SEP event starting on 7 January 2014 and lasting ∼ 3 days, which also had a solar energetic electron (SEE) event occurring simultaneously, BARREL had 6 payloads afloat spanning all MLT sectors and L-values. Three payloads were in a tight array (∼ 2 hrs in MLT and ∼ 2 Δ L) inside the inner magnetosphere and at times conjugate in both L and MLT with the Van Allen Pr. . .
Date: 04/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2016JA022462 Available at: http://doi.wiley.com/10.1002/2016JA022462http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016JA022462
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Authors: Maldonado Armando A., Chen Lunjin, Claudepierre Seth G., Bortnik Jacob, Thorne Richard M, et al.
Title: Electron butterfly distribution modulation by magnetosonic waves
Abstract: The butterfly pitch angle distribution is observed as a dip in an otherwise normal distribution of electrons centered about αeq=90°. During storm times, the formation of the butterfly distribution on the nightside magnetosphere has been attributed to L shell splitting combined with magnetopause shadowing and strong positive radial flux gradients. It has been shown that this distribution can be caused by combined chorus and magnetosonic wave scattering where the two waves work together but at different local times. Presented in our study is an event on 21 August 2013, using Van Allen Probe measurements, where a butterfly distribution formation is modulated by local magnetosonic coherent magnetosonic waves intensity. Transition from normal to butterfly distributions coincides with rising m. . .
Date: 04/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL068161 Available at: http://doi.wiley.com/10.1002/2016GL068161http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016GL068161http://api.wiley.com/onlinelibrary/chorus/v1/articles/10.1002%2F2016GL068161
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Authors: Li Jinxing, Ni Binbin, Ma Qianli, Xie Lun, Pu Zuyin, et al.
Title: Formation of Energetic Electron Butterfly Distributions by Magnetosonic Waves via Landau Resonance
Abstract: Radiation belt electrons can exhibit different types of pitch angle distributions in response to various magnetospheric processes. Butterfly distributions, characterized by flux minima at pitch angles around 90°, are broadly observed in both the outer and inner belts and the slot region. Butterfly distributions close to the outer magnetospheric boundary have been attributed to drift shell splitting and losses to the magnetopause. However, their occurrence in the inner belt and the slot region has hitherto not been resolved. By analyzing the particle and wave data collected by the Van Allen Probes during a geomagnetic storm, we combine test particle calculations and Fokker-Planck simulations to reveal that scattering by equatorial magnetosonic waves is a significant cause for the formation. . .
Date: 04/2016 Publisher: Geophysical Research Letters Pages: n/a - n/a DOI: 10.1002/2016GL067853 Available at: http://doi.wiley.com/10.1002/2016GL067853http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016GL067853
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Authors: Souza V. M., Vieira L. E. A., Medeiros C., Da Silva L. A., Alves L. R., et al.
Title: A neural network approach for identifying particle pitch angle distributions in Van Allen Probes data
Abstract: Analysis of particle pitch angle distributions (PADs) has been used as a means to comprehend a multitude of different physical mechanisms that lead to flux variations in the Van Allen belts and also to particle precipitation into the upper atmosphere. In this work we developed a neural network-based data clustering methodology that automatically identifies distinct PAD types in an unsupervised way using particle flux data. One can promptly identify and locate three well-known PAD types in both time and radial distance, namely, 90° peaked, butterfly, and flattop distributions. In order to illustrate the applicability of our methodology, we used relativistic electron flux data from the whole month of November 2014, acquired from the Relativistic Electron-Proton Telescope instrument on board. . .
Date: 04/2016 Publisher: Space Weather Pages: n/a - n/a DOI: 10.1002/2015SW001349 Available at: http://doi.wiley.com/10.1002/2015SW001349http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015SW001349
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Authors: Artemyev Anton, Agapitov Oleksiy, Mourenas Didier, Krasnoselskikh Vladimir, Shastun Vital, et al.
Title: Oblique Whistler-Mode Waves in the Earth’s Inner Magnetosphere: Energy Distribution, Origins, and Role in Radiation Belt Dynamics
Abstract: In this paper we review recent spacecraft observations of oblique whistler-mode waves in the Earth’s inner magnetosphere as well as the various consequences of the presence of such waves for electron scattering and acceleration. In particular, we survey the statistics of occurrences and intensity of oblique chorus waves in the region of the outer radiation belt, comprised between the plasmapause and geostationary orbit, and discuss how their actual distribution may be explained by a combination of linear and non-linear generation, propagation, and damping processes. We further examine how such oblique wave populations can be included into both quasi-linear diffusion models and fully nonlinear models of wave-particle interaction. On this basis, we demonstrate that varying amounts of obliq. . .
Date: 04/2016 Publisher: Space Science Reviews Pages: 261 - 355 DOI: 10.1007/s11214-016-0252-5 Available at: https://link.springer.com/article/10.1007/s11214-016-0252-5
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Authors: Zhao H., Li X, Baker D N, Claudepierre S G, Fennell J. F., et al.
Title: Ring current electron dynamics during geomagnetic storms based on the Van Allen Probes measurements
Abstract: Based on comprehensive measurements from Helium, Oxygen, Proton, and Electron Mass Spectrometer Ion Spectrometer, Relativistic Electron-Proton Telescope, and Radiation Belt Storm Probes Ion Composition Experiment instruments on the Van Allen Probes, comparative studies of ring current electrons and ions are performed and the role of energetic electrons in the ring current dynamics is investigated. The deep injections of tens to hundreds of keV electrons and tens of keV protons into the inner magnetosphere occur frequently; after the injections the electrons decay slowly in the inner belt but protons in the low L region decay very fast. Intriguing similarities between lower energy protons and higher-energy electrons are also found. The evolution of ring current electron and ion energy densi. . .
Date: 04/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: 3333 - 3346 DOI: 10.1002/2016JA022358 Available at: http://doi.wiley.com/10.1002/2016JA022358
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Authors: Li Jinxing, Bortnik Jacob, Thorne Richard M, Li Wen, Ma Qianli, et al.
Title: Ultrarelativistic electron butterfly distributions created by parallel acceleration due to magnetosonic waves
Abstract: The Van Allen Probe observations during the recovery phase of a large storm that occurred on 17 March 2015 showed that the ultrarelativistic electrons at the inner boundary of the outer radiation belt (L* = 2.6–3.7) exhibited butterfly pitch angle distributions, while the inner belt and the slot region also showed evidence of sub-MeV electron butterfly distributions. Strong magnetosonic waves were observed in the same regions and at the same time periods as these butterfly distributions. Moreover, when these magnetosonic waves extended to higher altitudes (L* = 4.1), the butterfly distributions also extended to the same region. Combining test particle calculations and Fokker-Planck diffusion simulations, we successfully reproduced the formation of the ultrarelativistic electron b. . .
Date: 04/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: 3212 - 3222 DOI: 10.1002/2016JA022370 Available at: http://doi.wiley.com/10.1002/2016JA022370
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Authors: Zhou Xu-Zhi, Wang Zi-Han, Zong Qiu-Gang, Rankin Robert, Kivelson Margaret G., et al.
Title: Charged particle behavior in the growth and damping stages of ultralow frequency waves: theory and Van Allen Probes observations
Abstract: Ultralow frequency (ULF) electromagnetic waves in Earth's magnetosphere can accelerate charged particles via a process called drift resonance. In the conventional drift-resonance theory, a default assumption is that the wave growth rate is time-independent, positive, and extremely small. However, this is not the case for ULF waves in the real magnetosphere. The ULF waves must have experienced an earlier growth stage when their energy was taken from external and/or internal sources, and as time proceeds the waves have to be damped with a negative growth rate. Therefore, a more generalized theory on particle behavior during different stages of ULF wave evolution is required. In this paper, we introduce a time-dependent imaginary wave frequency to accommodate the growth and damping of the wav. . .
Date: 03/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2016JA022447 Available at: http://doi.wiley.com/10.1002/2016JA022447http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016JA022447
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Authors: Selesnick R. S., Baker D N, Jaynes A. N., Li X, Kanekal S G, et al.
Title: Inward diffusion and loss of radiation belt protons
Abstract: Radiation belt protons in the kinetic energy range 24 to 76 MeV are being measured by the Relativistic Electron Proton Telescope on each of the two Van Allen Probes. Data have been processed for the purpose of studying variability in the trapped proton intensity during October 2013 to August 2015. For the lower energies (≲32 MeV), equatorial proton intensity near L = 2 showed a steady increase that is consistent with inward diffusion of trapped solar protons, as shown by positive radial gradients in phase space density at fixed values of the first two adiabatic invariants. It is postulated that these protons were trapped with enhanced efficiency during the 7 March 2012 solar proton event. A model that includes radial diffusion, along with known trapped proton source and loss processes, s. . .
Date: 03/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA022154 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015JA022154/full
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Authors: Zheng Hao, Holzworth Robert H., Brundell James B., Jacobson Abram R., Wygant John R., et al.
Title: A Statistical Study of Whistler Waves Observed by Van Allen Probes (RBSP) and Lightning Detected by WWLLN
Abstract: Lightning-generated whistler waves are electromagnetic plasma waves in the very low frequency (VLF) band, which play an important role in the dynamics of radiation belt particles. In this paper, we statistically analyze simultaneous waveform data from the Van Allen Probes (Radiation Belt Storm Probes, RBSP) and global lightning data from the World Wide Lightning Location Network (WWLLN). Data were obtained between July to September 2013 and between March and April 2014. For each day during these periods, we predicted the most probable 10 min for which each of the two RBSP satellites would be magnetically conjugate to lightning producing regions. The prediction method uses integrated WWLLN stroke data for that day obtained during the three previous years. Using these predicted times for mag. . .
Date: 03/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA022010 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA022010/full
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Authors: Gkioulidou Matina, Ukhorskiy A., Mitchell D G, and Lanzerotti L J
Title: Storm-time dynamics of ring current protons: Implications for the long-term energy budget in the inner magnetosphere
Abstract: Our investigation of the long-term ring current proton pressure evolution in Earth's inner magnetosphere based on Van Allen Probes data shows drastically different behavior of the low- and high- energy components of the ring current proton population with respect to the Sym-H index variation. We found that while the low-energy component of the protons (<80 keV) is strongly governed by convective timescales and is very well correlated with the absolute value of Sym-H index, the high-energy component (>100 keV) varies on much longer timescales and shows either no or anti-correlation with the absolute value of Sym-H index. Our study also shows that the contributions of the low- and high- energy protons to the inner magnetosphere energy content are comparable. Thus, our results conclusivel. . .
Date: 03/2016 Publisher: Geophysical Research Letters Pages: n/a - n/a DOI: 10.1002/2016GL068013 Available at: http://doi.wiley.com/10.1002/2016GL068013http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016GL068013
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Authors: Morley Steven K., Sullivan John P., Henderson Michael G., Blake Bernard, and Baker Daniel N
Title: The Global Positioning System constellation as a space weather monitor: Comparison of electron measurements with Van Allen Probes data
Abstract: Energetic electron observations in Earth's radiation belts are typically sparse and multi-point studies often rely on serendipitous conjunctions. This paper establishes the scientific utility of the Combined X-ray Dosimeter (CXD), currently flown on 19 satellites in the Global Positioning System (GPS) constellation, by cross-calibrating energetic electron measurements against data from the Van Allen Probes. By breaking our cross-calibration into two parts – one that removes any spectral assumptions from the CXD flux calculation, and one that compares the energy spectra – we first validate the modeled instrument response functions, then the calculated electron fluxes. Unlike previous forward modeling of energetic electron spectra we use a combination of four distributions that, together. . .
Date: 02/2016 Publisher: Space Weather DOI: 10.1002/2015SW001339 Available at: http://doi.wiley.com/10.1002/2015SW001339
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Authors: Gao Zhonglei, Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, et al.
Title: Intense low-frequency chorus waves observed by Van Allen Probes: Fine structures and potential effect on radiation belt electrons
Abstract: Frequency distribution is a vital factor in determining the contribution of whistler-mode chorus to radiation belt electron dynamics. Chorus is usually considered to occur in the frequency range 0.1–0.8 inline image (with the equatorial electron gyrofrequency inline image). We here report an event of intense low-frequency chorus with nearly half of wave power distributed below 0.1 inline image observed by Van Allen Probe A on 27 August 2014. This emission propagated quasi-parallel to the magnetic field and exhibited hiss-like signatures most of the time. The low-frequency chorus can produce the rapid loss of low-energy (∼0.1 MeV) electrons, different from the normal chorus. For high-energy (≥0.5 MeV) electrons, the low-frequency chorus can yield comparable momentum diffusion to tha. . .
Date: 02/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL067687 Available at: http://doi.wiley.com/10.1002/2016GL067687
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Authors: Orlova Ksenia, Shprits Yuri, and Spasojevic Maria
Title: New global loss model of energetic and relativistic electrons based on Van Allen Probes measurements
Abstract: Energetic electron observations in Earth's radiation belts are typically sparse and multi-point studies often rely on serendipitous conjunctions. This paper establishes the scientific utility of the Combined X-ray Dosimeter (CXD), currently flown on 19 satellites in the Global Positioning System (GPS) constellation, by cross-calibrating energetic electron measurements against data from the Van Allen Probes. By breaking our cross-calibration into two parts – one that removes any spectral assumptions from the CXD flux calculation, and one that compares the energy spectra – we first validate the modeled instrument response functions, then the calculated electron fluxes. Unlike previous forward modeling of energetic electron spectra we use a combination of four distributions that, together. . .
Date: 02/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021878 Available at: http://doi.wiley.com/10.1002/2015JA021878
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Authors: Andreeva Varvara A., and Tsyganenko Nikolai A.
Title: Reconstructing the magnetosphere from data using radial basis functions
Abstract: A new method is proposed to derive from data magnetospheric magnetic field configurations without any a priori assumptions on the geometry of electric currents. The approach utilizes large sets of archived satellite data and uses an advanced technique to represent the field as a sum of toroidal and poloidal parts, whose generating potentials Ψ1 and Ψ2 are expanded into series of radial basis functions (RBF) with their nodes regularly distributed over the 3D modeling domain. The method was tested by reconstructing the inner and high-latitude field within geocentric distances up to 12RE on the basis of magnetometer data of Geotail, Polar, Cluster, THEMIS, and Van Allen space probes, taken during 1995–2015. Four characteristic states of the magnetosphere before and during a disturbance ha. . .
Date: 02/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA022242 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA022242/full
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Authors: Kurita Satoshi, Miyoshi Yoshizumi, Blake Bernard, Reeves Geoffery D., and Kletzing Craig A.
Title: Relativistic electron microbursts and variations in trapped MeV electron fluxes during the 8-9 October 2012 storm: SAMPEX and Van Allen Probes observations
Abstract: It has been suggested that whistler mode chorus is responsible for both acceleration of MeV electrons and relativistic electron microbursts through resonant wave-particle interactions. Relativistic electron microbursts have been considered as an important loss mechanism of radiation belt electrons. Here we report on the observations of relativistic electron microbursts and flux variations of trapped MeV electrons during the 8–9 October 2012 storm, using the SAMPEX and Van Allen Probes satellites. Observations by the satellites show that relativistic electron microbursts correlate well with the rapid enhancement of trapped MeV electron fluxes by chorus wave-particle interactions, indicating that acceleration by chorus is much more efficient than losses by microbursts during the storm. It . . .
Date: 02/2016 Publisher: Geophysical Research Letters Pages: n/a - n/a DOI: 10.1002/2016GL068260 Available at: http://doi.wiley.com/10.1002/2016GL068260http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016GL068260
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Authors: Sarno-Smith Lois K., Larsen Brian A., Skoug Ruth M., Liemohn Michael W., Breneman Aaron, et al.
Title: Spacecraft surface charging within geosynchronous orbit observed by the Van Allen Probes
Abstract: Using the Helium Oxygen Proton Electron (HOPE) and Electric Field and Waves (EFW) instruments from the Van Allen Probes, we explored the relationship between electron energy fluxes in the eV and keV ranges and spacecraft surface charging. We present statistical results on spacecraft charging within geosynchronous orbit by L and MLT. An algorithm to extract the H+ charging line in the HOPE instrument data was developed to better explore intense charging events. Also, this study explored how spacecraft potential relates to electron number density, electron pressure, electron temperature, thermal electron current, and low-energy ion density between 1 and 210 eV. It is demonstrated that it is imperative to use both EFW potential measurements and the HOPE instrument ion charging line for examin. . .
Date: 02/2016 Publisher: Space Weather Pages: n/a - n/a DOI: 10.1002/2015SW001345 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015SW001345/full
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Authors: Boardsen Scott A, Hospodarsky George B, Kletzing Craig, Engebretson Mark, Pfaff Robert F, et al.
Title: Survey of the Frequency Dependent Latitudinal Distribution of the Fast Magnetosonic Wave Mode from Van Allen Probes EMFISIS Wave Form Receiver Plasma Wave Analysis
Abstract: We present a statistical survey of the latitudinal structure of the fast magnetosonic wave mode detected by the Van Allen Probes spanning the time interval of 9/21/2012 to 8/1/2014. We show that statistically the latitudinal occurrence of the wave frequency (f) normalized by the local proton cyclotron frequency (fcP) has a distinct funnel shaped appearance in latitude about the magnetic equator similar to that found in case studies. By comparing the observed E/B ratios with the model E/B ratio, using the observed plasma density and background magnetic field magnitude as input to the model E/B ratio, we show that this mode is consistent with the extraordinary (whistler) mode at wave normal angles (θk) near 90°. Performing polarization analysis on synthetic waveforms composed from a superp. . .
Date: 02/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA021844 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA021844/full
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Authors: Osmane Adnane, III Lynn B. Wilson, Blum Lauren, and Pulkkinen Tuija I.
Title: On the Connection Between Microbursts and Nonlinear Electronic Structures in Planetary Radiation Belts
Abstract: Using a dynamical-system approach, we have investigated the efficiency of large-amplitude whistler waves for causing microburst precipitation in planetary radiation belts by modeling the microburst energy and particle fluxes produced as a result of nonlinear wave–particle interactions. We show that wave parameters, consistent with large-amplitude oblique whistlers, can commonly generate microbursts of electrons with hundreds of keV-energies as a result of Landau trapping. Relativistic microbursts (>1 MeV) can also be generated by a similar mechanism, but require waves with large propagation angles ${\theta }_{{kB}}\gt 50^\circ$ and phase-speeds ${v}_{{\rm{\Phi }}}\geqslant c/9$. Using our result for precipitating density and energy fluxes, we argue that holes in the distribution functio. . .
Date: 01/2016 Publisher: The Astrophysical Journal Pages: 51 DOI: 10.3847/0004-637X/816/2/51 Available at: http://stacks.iop.org/0004-637X/816/i=2/a=51?key=crossref.70d237eeae19ada88cf791dd9ba676be
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Authors: Pierrard V., and Rosson G.
Title: The effects of the big storm events in the first half of 2015 on the radiation belts observed by EPT/PROBA-V
Abstract: With the energetic particle telescope (EPT) performing with direct electron and proton discrimination on board the ESA satellite PROBA-V, we analyze the high-resolution measurements of the charged particle radiation environment at an altitude of 820 km for the year 2015. On 17 March 2015, a big geomagnetic storm event injected unusual fluxes up to low radial distances in the radiation belts. EPT electron measurements show a deep dropout at L > 4 starting during the main phase of the storm, associated to the penetration of high energy fluxes at L < 2 completely filling the slot region. After 10 days, the formation of a new slot around L = 2.8 for electrons of 500–600 keV separates the outer belt from the belt extending at other longitudes than the South Atlantic Anomaly. Two oth. . .
Date: 01/2016 Publisher: Annales Geophysicae Pages: 75 - 84 DOI: 10.5194/angeo-34-75-2016 Available at: http://www.ann-geophys.net/34/75/2016/
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Authors: Mozer F S, Artemyev A., Agapitov O. V., Mourenas D., and Vasko I.
Title: Near-Relativistic Electron Acceleration by Landau Trapping in Time Domain Structures
Abstract: Data from the Van Allen Probes have provided the first extensive evidence of nonlinear (as opposed to quasi-linear) wave-particle interactions in space with the associated rapid (less than a bounce period) electron acceleration to hundreds of keV by Landau resonance in the parallel electric field of time domain structures (TDSs) traveling at high speeds (~20,000 km/s). This observational evidence is supported by simulations and discussion of the source and spatial extent of the fast TDS. This result indicates the possibility that the electrostatic fields in TDS may generate the electron seed population for cyclotron resonance interaction with chorus waves to make higher-energy electrons.
Date: 01/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL067316 Available at: http://doi.wiley.com/10.1002/2015GL067316
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Authors: Matsui H., Paulson K. W., Torbert R B, Spence H E, Kletzing C A, et al.
Title: Nonlinearity in chorus waves during a geomagnetic storm on 1 November 2012
Abstract: In this study, we investigate the possibility of nonlinearity in chorus waves during a geomagnetic storm on 1 November 2012. The data we use were measured by the Van Allen Probe B. Wave data and plasma sheet electron data are analyzed. Chorus waves were frequently measured in the morning side during the main phase of this storm. Large-amplitude chorus waves were seen of the order of ∼0.6 nT and >7 mV/m, which are similar to or larger than the typical ULF waves. The waves quite often consist of rising tones during the burst sampling. Since the rising tone is known as a signature of nonlinearity, a large portion of the waves are regarded as nonlinear at least during the burst sampling periods. These results underline the importance of nonlinearity in the dynamics of chorus waves. We furthe. . .
Date: 01/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021772 Available at: http://doi.wiley.com/10.1002/2015JA021772
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Authors: Sigsbee K., Kletzing C A, Smith C W, MacDowall Robert, Spence Harlan, et al.
Title: Van Allen Probes, THEMIS, GOES, and Cluster Observations of EMIC waves, ULF pulsations, and an electron flux dropout
Abstract: We examined an electron flux dropout during the 12–14 November 2012 geomagnetic storm using observations from seven spacecraft: the two Van Allen Probes, THEMIS-A (P5), Cluster 2, and Geostationary Operational Environmental Satellite (GOES) 13, 14, and 15. The electron fluxes for energies greater than 2.0 MeV observed by GOES 13, 14, and 15 at geosynchronous orbit and by the Van Allen Probes remained at or near instrumental background levels for more than 24 hours from 12–14 November. For energies of 0.8 MeV, the GOES satellites observed two shorter intervals of reduced electron fluxes. The first interval of reduced 0.8 MeV electron fluxes on 12–13 November was associated with an interplanetary shock and a sudden impulse. Cluster, THEMIS, and GOES observed intense He+ EMIC wa. . .
Date: 01/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020877 Available at: http://doi.wiley.com/10.1002/2014JA020877
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Authors: Matsuda Shoya, Kasahara Yoshiya, and Kletzing Craig A.
Title: Variation in crossover frequency of EMIC waves in plasmasphere estimated from ion cyclotron whistler waves observed by Van Allen Probe A
Abstract: We report variations in the propagation of the H+ band ion cyclotron whistlers observed by Van Allen Probe A. Ion cyclotron whistlers are one of the EMIC (electromagnetic ion cyclotron) waves generated by mode conversion from lightning whistlers. Crossover frequency is an important frequency for the ion cyclotron whistlers, which is a function of the variations in the local heavy-ion composition. We surveyed waveform data obtained by the Electric and Magnetic Field Instrument and Integrated Science instrument and found that 3461 H+ band ion cyclotron whistlers were observed from 572 km to 5992 km in altitude. The main finding is that the crossover frequencies of the observed events decreased with increasing altitude. These results support the hypothesis that the total heavy-ion density dec. . .
Date: 01/2016 Publisher: Geophysical Research Letters Pages: 28 - 34 DOI: 10.1002/2015GL066893 Available at: http://doi.wiley.com/10.1002/2015GL066893
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Authors: Lejosne Solène, and Roederer Juan G.
Title: The “zebra stripes”: An effect of F-region zonal plasma drifts on the longitudinal distribution of radiation belt particles
Abstract: We examine a characteristic effect, namely, the ubiquitous appearance of structured peaks and valleys called zebra stripes in the spectrograms of energetic electrons and ions trapped in the inner belt below L ~ 3. We propose an explanation of this phenomenon as a purely kinematic consequence of particle drift velocity modulation caused by F region zonal plasma drifts in the ionosphere. In other words, we amend the traditional assumption that the electric field associated with ionospheric plasma drives trapped particle distributions into rigid corotation with the Earth. An equation based on a simple first-order model is set up to determine quantitatively the appearance of zebra stripes as a function of magnetic time. Our numerical predictions are in agreement with measurements by the Ra. . .
Date: 01/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021925 Available at: http://doi.wiley.com/10.1002/2015JA021925
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2015
Authors: Ma Qianli, Li Wen, Thorne Richard M, Bortnik Jacob, Kletzing C A, et al.
Title: Electron scattering by magnetosonic waves in the inner magnetosphere
Abstract: We investigate the importance of electron scattering by magnetosonic waves in the Earth's inner magnetosphere. A statistical survey of the magnetosonic wave amplitude and wave frequency spectrum, as a function of geomagnetic activity, is performed using the Van Allen Probes wave measurements, and is found to be generally consistent with the wave distribution obtained from previous spacecraft missions. Outside the plasmapause the statistical frequency distribution of magnetosonic waves follows the variation of the lower hybrid resonance frequency, but this trend is not observed inside the plasmasphere. Drift and bounce averaged electron diffusion rates due to magnetosonic waves are calculated using a recently developed analytical formula. The resulting time scale of electron energization du. . .
Date: 12/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021992 Available at: http://doi.wiley.com/10.1002/2015JA021992http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021992
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Authors: Reeves Geoffrey D, Friedel Reiner H W, Larsen Brian A., Skoug Ruth M., Funsten Herbert O., et al.
Title: Energy dependent dynamics of keV to MeV electrons in the inner zone, outer zone, and slot regions.
Abstract: We present observations of the radiation belts from the HOPE and MagEIS particle detectors on the Van Allen Probes satellites that illustrate the energy-dependence and L-shell dependence of radiation belt enhancements and decays. We survey events in 2013 and analyze an event on March 1 in more detail. The observations show: (a) At all L-shells, lower-energy electrons are enhanced more often than higher energies; (b) Events that fill the slot region are more common at lower energies; (c) Enhancements of electrons in the inner zone are more common at lower energies; and (d) Even when events do not fully fill the slot region, enhancements at lower-energies tend to extend to lower L-shells than higher energies. During enhancement events the outer zone extends to lower L-shells at lower energie. . .
Date: 12/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021569 Available at: http://doi.wiley.com/10.1002/2015JA021569http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021569
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Authors: Agapitov O. V., Artemyev A. V., Mourenas D., Mozer F S, and Krasnoselskikh V.
Title: Nonlinear local parallel acceleration of electrons through Landau trapping by oblique whistler mode waves in the outer radiation belt
Abstract: Simultaneous observations of electron velocity distributions and chorus waves by the Van Allen Probe B are analyzed to identify long-lasting (more than 6 h) signatures of electron Landau resonant interactions with oblique chorus waves in the outer radiation belt. Such Landau resonant interactions result in the trapping of ∼1–10 keV electrons and their acceleration up to 100–300 keV. This kind of process becomes important for oblique whistler mode waves having a significant electric field component along the background magnetic field. In the inhomogeneous geomagnetic field, such resonant interactions then lead to the formation of a plateau in the parallel (with respect to the geomagnetic field) velocity distribution due to trapping of electrons into the wave effective potential. We de. . .
Date: 12/2015 Publisher: Geophysical Research Letters Pages: 10,140 - 10,149 DOI: 10.1002/2015GL066887 Available at: http://doi.wiley.com/10.1002/2015GL066887http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015GL066887
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Authors: Shi Run, Summers Danny, Ni Binbin, Fennell Joseph F., Blake Bernard, et al.
Title: Survey of radiation belt energetic electron pitch angle distributions based on the Van Allen Probes MagEIS measurements
Abstract: A statistical survey of electron pitch angle distributions (PADs) is performed based on the pitch angle resolved flux observations from the Magnetic Electron Ion Spectrometer (MagEIS) instrument on board the Van Allen Probes during the period from 1 October 2012 to 1 May 2015. By fitting the measured PADs to a sinnα form, where α is the local pitch angle and n is the power law index, we investigate the dependence of PADs on electron kinetic energy, magnetic local time (MLT), the geomagnetic Kp index and L-shell. The difference in electron PADs between the inner and outer belt is distinct. In the outer belt, the common averaged n values are less than 1.5, except for large values of the Kp index and high electron energies. The averaged n values vary considerably with MLT, with a peak in th. . .
Date: 12/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021724 Available at: http://doi.wiley.com/10.1002/2015JA021724http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021724
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Authors: Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zong Q.-G., Zhou X.-Z., et al.
Title: Ultra-low-frequency wave-driven diffusion of radiation belt relativistic electrons
Abstract: Van Allen radiation belts are typically two zones of energetic particles encircling the Earth separated by the slot region. How the outer radiation belt electrons are accelerated to relativistic energies remains an unanswered question. Recent studies have presented compelling evidence for the local acceleration by very-low-frequency (VLF) chorus waves. However, there has been a competing theory to the local acceleration, radial diffusion by ultra-low-frequency (ULF) waves, whose importance has not yet been determined definitively. Here we report a unique radiation belt event with intense ULF waves but no detectable VLF chorus waves. Our results demonstrate that the ULF waves moved the inner edge of the outer radiation belt earthward 0.3 Earth radii and enhanced the relativistic electron fl. . .
Date: 12/2015 Publisher: Nature Communications Pages: 10096 DOI: 10.1038/ncomms10096 Available at: http://www.nature.com/doifinder/10.1038/ncomms10096
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Authors: Agapitov O. V., Mozer F. S., Artemyev A. V., Mourenas D., and Krasnoselskikh V. V.
Title: Wave-particle interactions in the outer radiation belts
Abstract: Data from the Van Allen Probes have provided the first extensive evidence of non-linear (as opposed to quasi-linear) wave-particle interactions in space, with the associated rapid (fraction of a bounce period) electron acceleration, to hundreds of keV by Landau resonance, in the parallel electric fields of time domain structures (TDS) and very oblique chorus waves. The experimental evidence, simulations, and theories of these processes are discussed.
Date: 12/2015 Publisher: Advances in Astronomy and Space Physics Pages: 68-74 DOI: N/A Available at: http://aasp.kiev.ua/volume5/068-074-Agapitov.pdf
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Authors: Spasojevic M., Shprits Y.Y., and Orlova K.
Title: Global Empirical Models of Plasmaspheric Hiss using Van Allen Probes
Abstract: Plasmaspheric hiss is a whistler mode emission that permeates the Earth's plasmasphere and is a significant driver of energetic electron losses through cyclotron-resonant pitch angle scattering. The EMFISIS instrument on the Van Allen Probes mission provides vastly improved measurements of the hiss wave environment including continuous measurements of the wave magnetic field cross-spectral matrix and enhanced low frequency coverage. Here, we develop empirical models of hiss wave intensity using two years of Van Allen Probes data. First, we describe the construction of the hiss database. Then, we compare the hiss spectral distribution and integrated wave amplitude obtained from Van Allen Probes to those previously extracted from the CRRES mission. Next, we develop a cubic regression model o. . .
Date: 11/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA021803 Available at: http://doi.wiley.com/10.1002/2015JA021803http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021803
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Authors: Rodger Craig J., Hendry Aaron T., Clilverd Mark A., Kletzing Craig A., Brundell James B., et al.
Title: High-resolution in situ observations of electron precipitation-causing EMIC waves
Abstract: Electromagnetic ion cyclotron (EMIC) waves are thought to be important drivers of energetic electron losses from the outer radiation belt through precipitation into the atmosphere. While the theoretical possibility of pitch angle scattering-driven losses from these waves has been recognized for more than four decades, there have been limited experimental precipitation observations to support this concept. We have combined satellite-based observations of the characteristics of EMIC waves, with satellite and ground-based observations of the EMIC-induced electron precipitation. In a detailed case study, supplemented by an additional four examples, we are able to constrain for the first time the location, size, and energy range of EMIC-induced electron precipitation inferred from coincident pr. . .
Date: 11/2015 Publisher: Geophysical Research Letters Pages: 9633 - 9641 DOI: 10.1002/grl.v42.2210.1002/2015GL066581 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015GL066581/full
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Authors: Srinivasan Dipak K., Adams Norm, and Wallis Robert
Title: In-flight performance of the Van Allen Probes RF telecommunications system
Abstract: The NASA Van Allen Probes mission (previously called the Radiation Belt Storm Probes) successfully launched on 30 August 2012. The twin spacecraft, designed, built, and operated by The Johns Hopkins University Applied Physics Laboratory (JHU/APL), has been successfully operating within Earth׳s radiation belts since then, returning critical science data revealing new insights into the physics of the radiation belts. Because of the extreme radiation environment, all spacecraft subsystems including the communications system had to make special accommodations to withstand the effects of the radiation. Each Van Allen Probes spacecraft׳s telecommunications system includes an S-band version of the Frontier Radio, a solid-state power amplifier, RF routing components, and dual low-gain antenna. . .
Date: 11/2015 Publisher: Acta Astronautica Pages: 211 - 221 DOI: 10.1016/j.actaastro.2015.05.001 Available at: http://www.sciencedirect.com/science/article/pii/S0094576515001824
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Authors: Malaspina David M., Claudepierre Seth G., Takahashi Kazue, Jaynes Allison N., Elkington Scot R, et al.
Title: Kinetic Alfvén Waves and Particle Response Associated with a Shock-Induced, Global ULF Perturbation of the Terrestrial Magnetosphere
Abstract: On 2 October 2013, the arrival of an interplanetary shock compressed the Earth's magnetosphere and triggered a global ULF (ultra low frequency) oscillation. The Van Allen Probe B spacecraft observed this large-amplitude ULF wave in situ with both magnetic and electric field data. Broadband waves up to approximately 100 Hz were observed in conjunction with, and modulated by, this ULF wave. Detailed analysis of fields and particle data reveals that these broadband waves are Doppler-shifted kinetic Alfvén waves. This event suggests that magnetospheric compression by interplanetary shocks can induce abrupt generation of kinetic Alfvén waves over large portions of the inner magnetosphere, potentially driving previously unconsidered wave-particle interactions throughout the inner magnetosphere. . .
Date: 11/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL065935 Available at: http://doi.wiley.com/10.1002/2015GL065935http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015GL065935
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Authors: Takahashi Kazue, Waters Colin, Glassmeier Karl-Heinz, Kletzing Craig, Kurth William, et al.
Title: Multifrequency compressional magnetic field oscillations and their relation to multiharmonic toroidal mode standing Alfvén waves
Abstract: The power spectrum of the compressional component of magnetic fields observed by the Van Allen Probes spacecraft near the magnetospheric equator in the dayside plasmasphere sometimes exhibits regularly spaced multiple peaks at frequencies below 50 mHz. We show by detailed analysis of events observed on two separate days in early 2014 that the frequencies change smoothly with the radial distance of the spacecraft and appear at or very near the frequencies of the odd harmonics of mutiharmonic toroidal mode standing Alfvén waves seen in the azimuthal component of the magnetic field. Even though the compressional component had a low amplitude on one of the selected days, its spectral properties are highlighted by computing the ratio of the spectral powers of time series data obtained from two. . .
Date: 11/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021780 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015JA021780/abstract
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Authors: Yu J., Li L.Y., Cao J. B., Yuan Z. G., Reeves G D, et al.
Title: Multiple loss processes of relativistic electrons outside the heart of outer radiation belt during a storm sudden commencement
Abstract: By examining the compression-induced changes in the electron phase space density and pitch angle distribution observed by two satellites of Van Allen Probes (RBSP-A/B), we find that the relativistic electrons (>2MeV) outside the heart of outer radiation belt (L*≥ 5) undergo multiple losses during a storm sudden commencement (SSC). The relativistic electron loss mainly occurs in the field-aligned direction (pitch angle α< 30° or >150°), and the flux decay of the field-aligned electrons is independent of the spatial location variations of the two satellites. However, the relativistic electrons in the pitch angle range of 30°-150° increase (decrease) with the decreasing (increasing) geocentric distance (|ΔL|< 0.25) of the RBSP-B (RBSP-A) location, and the electron fluxes in the quasi-. . .
Date: 11/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021460 Available at: http://doi.wiley.com/10.1002/2015JA021460http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021460
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Authors: Sakaguchi Kaori, Nagatsuma Tsutomu, Reeves Geoffrey, and Spence Harlan E.
Title: Prediction of MeV electron fluxes throughout the outer radiation belt using multivariate autoregressive models
Abstract: The Van Allen radiation belts surrounding the Earth are filled with MeV-energy electrons. This region poses ionizing radiation risks for spacecraft that operate within it, including those in geostationary (GEO) and medium Earth orbit (MEO). To provide alerts of electron flux enhancements, sixteen prediction models of the electron log-flux variation throughout the equatorial outer radiation belt as a function of the McIlwain L parameter were developed using the multivariate autoregressive model and Kalman filter. Measurements of omni-directional 2.3 MeV electron flux from the Van Allen Probes mission as well as >2 MeV electrons from the GOES-15 spacecraft were used as the predictors. Model explanatory parameters were selected from solar wind parameters, the electron log-flux at GEO, and geo. . .
Date: 11/2015 Publisher: Space Weather Pages: n/a - n/a DOI: 10.1002/2015SW001254 Available at: http://doi.wiley.com/10.1002/2015SW001254http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015SW001254
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Authors: de Soria-Santacruz M., Li W, Thorne R M, Ma Q, Bortnik J, et al.
Title: Analysis of plasmaspheric hiss wave amplitudes inferred from low-altitude POES electron data: Validation with conjunctive Van Allen Probes observations
Abstract: Plasmaspheric hiss plays an important role in controlling the overall structure and dynamics of the Earth's radiation belts. The interaction of plasmaspheric hiss with radiation belt electrons is commonly evaluated using diffusion codes, which rely on statistical models of wave observations that may not accurately reproduce the instantaneous global wave distribution, or the limited in-situ satellite wave measurements from satellites. This paper evaluates the performance and limitations of a novel technique capable of inferring wave amplitudes from low-altitude electron flux observations from the POES spacecraft, which provide extensive coverage in L-shell and MLT. We found that, within its limitations, this technique could potentially be used to build a dynamic global model of the plasmasp. . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021148 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA021148/abstract
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Authors: Motoba T., Ohtani S, Anderson B J, Korth H., Mitchell D., et al.
Title: On the formation and origin of substorm growth phase/onset auroral arcs inferred from conjugate space-ground observations
Abstract: Magnetotail processes and structures related to substorm growth phase/onset auroral arcs remain poorly understood mostly due to the lack of adequate observations. In this study we make a comparison between ground-based optical measurements of the premidnight growth phase/onset arcs at subauroral latitudes and magnetically conjugate measurements made by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) at ~780 km in altitude and by the Van Allen Probe B (RBSP-B) spacecraft crossing L values of ~5.0–5.6 in the premidnight inner tail region. The conjugate observations offer a unique opportunity to examine the detailed features of the arc location relative to large-scale Birkeland currents and of the magnetospheric counterpart. Our main findings include (1. . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 8707 - 8722 DOI: 10.1002/jgra.v120.1010.1002/2015JA021676 Available at: http://doi.wiley.com/10.1002/jgra.v120.10http://doi.wiley.com/10.1002/2015JA021676http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021676
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Authors: Vasko I. Y., Agapitov O. V., Mozer F S, and Artemyev A. V.
Title: Thermal electron acceleration by electric field spikes in the outer radiation belt: Generation of field-aligned pitch angle distributions
Abstract: Van Allen Probes observations in the outer radiation belt have demonstrated an abundance of electrostatic electron-acoustic double layers (DL). DLs are frequently accompanied by field-aligned (bidirectional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV. We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e., due to reflections from DL potential humps. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi me. . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021644 Available at: http://doi.wiley.com/10.1002/2015JA021644http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021644
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Authors: Zhang J.-C., Kistler L. M., Spence H E, Wolf R. A., Reeves G., et al.
Title: “Trunk-like” heavy ion structures observed by the Van Allen Probes
Abstract: Dynamic ion spectral features in the inner magnetosphere are the observational signatures of ion acceleration, transport, and loss in the global magnetosphere. We report “trunk-like” ion structures observed by the Van Allen Probes on 2 November 2012. This new type of ion structure looks like an elephant's trunk on an energy-time spectrogram, with the energy of the peak flux decreasing Earthward. The trunks are present in He+ and O+ ions but not in H+. During the event, ion energies in the He+ trunk, located at L = 3.6–2.6, MLT = 9.1–10.5, and MLAT = −2.4–0.09°, vary monotonically from 3.5 to 0.04 keV. The values at the two end points of the O+ trunk are: energy = 4.5–0.7 keV, L = 3.6–2.5, MLT = 9.1–10.7, and MLAT = −2.4–0.4°. Results from backward ion drift path tra. . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021822 Available at: http://doi.wiley.com/10.1002/2015JA021822http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021822
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Authors: Chaston C. C., Bonnell J. W., Kletzing C A, Hospodarsky G B, Wygant J R, et al.
Title: Broadband low frequency electromagnetic waves in the inner magnetosphere
Abstract: A prominent yet largely unrecognized feature of the inner magnetosphere associated with particle injections, and more generally geomagnetic storms, is the occurrence of broadband electromagnetic field fluctuations over spacecraft frame frequencies (fsc) extending from effectively zero to fsc ≳ 100 Hz. Using observations from the Van Allen Probes we show that these waves most commonly occur pre-midnight but are observed over a range of local times extending into the dayside magnetosphere. We find that the variation of magnetic spectral energy density with fsc obeys inline image over several decades with a spectral break-point at fb ≈1 Hz. The values for α are log normally distributed with α = 1.9 ± 0.6 for fsc < fb andα = 2.9 ± 0.6 for fsc > fb. A is . . .
Date: 09/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021690 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015JA021690/abstract
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