Biblio

Found 909 results
2015
Authors: Li Haimeng, Yuan Zhigang, Yu Xiongdong, Huang Shiyong, Wang Dedong, et al.
Title: The enhancement of cosmic radio noise absorption due to hiss-driven energetic electron precipitation during substorms
Abstract: The Van-Allen probes, low-altitude NOAA satellite, MetOp satellite and riometer are used to analyze variations of precipitating energetic electron fluxes and cosmic radio noise absorption (CNA) driven by plasmaspheric hiss with respect to geomagnetic activities. The hiss-driven energetic electron precipitations (at L~4.7-5.3, MLT~8-9) are observed during geomagnetic quiet condition and substorms, respectively. We find that the CNA detected by riometers increased very little in the hiss-driven event during quiet condition on September 06, 2012. The hiss-driven enhancement of riometer was still little during the first substorm on September 30, 2012. However, the absorption detected by the riometer largely increased while the energies of the injected electrons became higher during the second . . .
Date: 06/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021113 Available at: http://doi.wiley.com/10.1002/2015JA021113
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Authors: Němec F., Santolik O, Hrbáčková Z., Pickett J. S., and Cornilleau-Wehrlin N.
Title: Equatorial noise emissions with quasiperiodic modulation of wave intensity
Abstract: Equatorial noise (EN) emissions are electromagnetic wave events at frequencies between the proton cyclotron frequency and the lower hybrid frequency observed in the equatorial region of the inner magnetosphere. They propagate nearly perpendicular to the ambient magnetic field, and they exhibit a harmonic line structure characteristic of the proton cyclotron frequency in the source region. However, they were generally believed to be continuous in time. We investigate more than 2000 EN events observed by the Spatio-Temporal Analysis of Field Fluctuations and Wide-Band Data Plasma Wave investigation instruments on board the Cluster spacecraft, and we show that this is not always the case. A clear quasiperiodic (QP) time modulation of the wave intensity is present in more than 5% of events. We. . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020816 Available at: http://doi.wiley.com/10.1002/2014JA020816
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Authors: Bin Kang Suk-, Min Kyoung-Wook, Fok Mei-Ching, Hwang Junga, and Choi Cheong-Rim
Title: Estimation of pitch angle diffusion rates and precipitation time scales of electrons due to EMIC waves in a realistic field model
Abstract: Electromagnetic ion cyclotron (EMIC) waves are closely related to precipitating loss of relativistic electrons in the radiation belts, and thereby, a model of the radiation belts requires inclusion of the pitch angle diffusion caused by EMIC waves. We estimated the pitch angle diffusion rates and the corresponding precipitation time scales caused by H and He band EMIC waves using the Tsyganenko 04 (T04) magnetic field model at their probable regions in terms of geomagnetic conditions. The results correspond to enhanced pitch angle diffusion rates and reduced precipitation time scales compared to those based on the dipole model, up to several orders of magnitude for storm times. While both the plasma density and the magnetic field strength varied in these calculations, the reduction of the . . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 8529 - 8546 DOI: 10.1002/2014JA020644 Available at: http://doi.wiley.com/10.1002/2014JA020644http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2014JA020644
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Authors: Ganguli G., Crabtree C., Mithaiwala M., Rudakov L., and Scales W.
Title: Evolution of lower hybrid turbulence in the ionosphere
Abstract: Three-dimensional evolution of the lower hybrid turbulence driven by a spatially localized ion ring beam perpendicular to the ambient magnetic field in space plasmas is analyzed. It is shown that the quasi-linear saturation model breaks down when the nonlinear rate of scattering by thermal electron is larger than linear damping rates, which can occur even for low wave amplitudes. The evolution is found to be essentially a three-dimensional phenomenon, which cannot be accurately explained by two-dimensional simulations. An important feature missed in previous studies of this phenom- enon is the nonlinear conversion of electrostatic lower hybrid waves into electromagnetic whistler and magnetosonic waves and the consequent energy loss due to radiation from the source region. This can result i. . .
Date: 11/2015 Publisher: Physics of Plasmas Pages: 112904 DOI: 10.1063/1.4936281 Available at: http://scitation.aip.org/content/aip/journal/pop/22/11/10.1063/1.4936281
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Authors: Zhao H., Li X, Baker D N, Fennell J. F., Blake J B, et al.
Title: The evolution of ring current ion energy density and energy content during geomagnetic storms based on Van Allen Probes measurements
Abstract: Enabled by the comprehensive measurements from the MagEIS, HOPE, and RBSPICE instruments onboard Van Allen Probes in the heart of the radiation belt, the relative contributions of ions with different energies and species to the ring current energy density and their dependence on the phases of geomagnetic storms are quantified. The results show that lower energy (<50 keV) protons enhance much more often and also decay much faster than higher energy protons. During the storm main phase, ions with energies < 50 keV contribute more significantly to the ring current than those with higher energies; while the higher energy protons dominate during the recovery phase and quiet times. The enhancements of higher energy proton fluxes as well as energy content generally occur later than those of lower. . .
Date: 08/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021533 Available at: http://doi.wiley.com/10.1002/2015JA021533
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Authors: Lugaz N., Farrugia C. J., Huang C.-L., and Spence H E
Title: Extreme geomagnetic disturbances due to shocks within CMEs
Abstract: We report on features of solar wind-magnetosphere coupling elicited by shocks propagating through coronal mass ejections (CMEs) by analyzing the intense geomagnetic storm of 6 August 1998. During this event, the dynamic pressure enhancement at the shock combined with a simultaneous increase in the southward component of the magnetic field resulted in a large earthward retreat of Earth's magnetopause, which remained close to geosynchronous orbit for more than 4 h. This occurred despite the fact that both shock and CME were weak and relatively slow. Another similar example of a weak shock inside a slow CME resulting in an intense geomagnetic storm is the 30 September 2012 event, which strongly depleted the outer radiation belt. We discuss the potential of shocks inside CMEs to cause large . . .
Date: 06/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL064530 Available at: http://doi.wiley.com/10.1002/2015GL064530
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Authors: Chaston C. C., Bonnell J. W., Wygant J R, Kletzing C A, Reeves G D, et al.
Title: Extreme ionospheric ion energization and electron heating in Alfvén waves in the storm-time inner magnetosphere
Abstract: We report measurements of energized outflowing/bouncing ionospheric ions and heated electrons in the inner magnetosphere during a geomagnetic storm. The ions arrive in the equatorial plane with pitch angles that increase with energy over a range from tens of eV to > 50 keV while the electrons are field-aligned up to ~1 keV. These particle distributions are observed during intervals of broadband low frequency electromagnetic field fluctuations consistent with a Doppler-shifted spectrum of kinetic Alfvén waves and kinetic field-line resonances. The fluctuations extend from L≈3 out to the apogee of the Van Allen Probes spacecraft at L≈6.5. They thereby span most of the L-shell range occupied by the ring current. These measurements suggest a model for ionospheric ion outflow and energizat. . .
Date: 12/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL066674 Available at: http://doi.wiley.com/10.1002/2015GL066674http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015GL066674
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Authors: Wang Chengrui, Rankin Robert, and Zong Qiugang
Title: Fast damping of ultralow frequency waves excited by interplanetary shocks in the magnetosphere
Abstract: Analysis of Cluster spacecraft data shows that intense ultralow frequency (ULF) waves in the inner magnetosphere can be excited by the impact of interplanetary shocks and solar wind dynamic pressure variations. The observations reveal that such waves can be damped away rapidly in a few tens of minutes. Here we examine mechanisms of ULF wave damping for two interplanetary shocks observed by Cluster on 7 November 2004 and 30 August 2001. The mechanisms considered are ionospheric joule heating, Landau damping, and waveguide energy propagation. It is shown that Landau damping provides the dominant ULF wave damping for the shock events of interest. It is further demonstrated that damping is caused by drift-bounce resonance with ions in the energy range of a few keV. Landau damping is shown to b. . .
Date: 03/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020761 Available at: http://doi.wiley.com/10.1002/2014JA020761
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Authors: Breuillard H., Agapitov O., Artemyev A., Kronberg E. A., Haaland S. E., et al.
Title: Field-aligned chorus wave spectral power in Earth's outer radiation belt
Abstract: Chorus-type whistler waves are one of the most intense electromagnetic waves generated naturally in the magnetosphere. These waves have a substantial impact on the radiation belt dynamics as they are thought to contribute to electron acceleration and losses into the ionosphere through resonant wave–particle interaction. Our study is devoted to the determination of chorus wave power distribution on frequency in a wide range of magnetic latitudes, from 0 to 40°. We use 10 years of magnetic and electric field wave power measured by STAFF-SA onboard Cluster spacecraft to model the initial (equatorial) chorus wave spectral power, as well as PEACE and RAPID measurements to model the properties of energetic electrons (~ 0.1–100 keV) in the outer radiation belt. The dependence of this distrib. . .
Date: 01/2015 Publisher: Annales Geophysicae Pages: 583 - 597 DOI: 10.5194/angeo-33-583-2015 Available at: http://www.ann-geophys.net/33/583/2015/http://www.ann-geophys.net/33/583/2015/angeo-33-583-2015.pdf
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Authors: Li W, Chen L, Bortnik J, Thorne R M, Angelopoulos V, et al.
Title: First Evidence for Chorus at a Large Geocentric Distance as a Source of Plasmaspheric Hiss: Coordinated THEMIS and Van Allen Probes Observation
Abstract: Recent ray tracing suggests that plasmaspheric hiss can originate from chorus observed outside of the plasmapause. Although a few individual events have been reported to support this mechanism, the number of reported conjugate events is still very limited. Using coordinated observations between THEMIS and Van Allen Probes, we report on an interesting event, where chorus was observed at a large L-shell (~9.8), different from previously reported events at L < 6, but still exhibited a remarkable correlation with hiss observed in the outer plasmasphere (L ~ 5.5). Ray tracing indicates that a subset of chorus can propagate into the observed location of hiss on a timescale of ~ 5-6 s, in excellent agreement with the observed time lag between chorus and hiss. This provides quantitative support th. . .
Date: 01/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062832 Available at: http://doi.wiley.com/10.1002/2014GL062832
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Authors: Valek P. W., Goldstein J, Jahn J -M, McComas D J, and Spence H E
Title: First joint in situ and global observations of the medium-energy oxygen and hydrogen in the inner magnetosphere
Abstract: We present the first simultaneous observations of the in situ ions and global Energetic Neutral Atom (ENA) images of the composition-separated, medium-energy (~1–50 keV) particle populations of the inner magnetosphere. The ENA emissions are mapped into L shell/magnetic local time space based on the exospheric density along the line of sight (LOS). The ENA measurement can then be scaled to determine an average ion flux along a given LOS. The in situ ion flux tends to be larger than the scaled ENAs at the same local time. This indicates that the ion population is more concentrated in the Van Allen Probes orbital plane than distributed along the Two Wide-angle Imaging Neutral-atom Spectrometers LOS. For the large storm of 14 November 2012, we observe that the concentration of O (in situ i. . .
Date: 09/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 7615 - 7628 DOI: 10.1002/2015JA021151 Available at: http://doi.wiley.com/10.1002/2015JA021151http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021151
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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: Nosé M., Oimatsu S., Keika K, Kletzing C A, Kurth W S, et al.
Title: Formation of the oxygen torus in the inner magnetosphere: Van Allen Probes observations
Abstract: We study the formation process of an oxygen torus during the 12–15 November 2012 magnetic storm, using the magnetic field and plasma wave data obtained by Van Allen Probes. We estimate the local plasma mass density (ρL) and the local electron number density (neL) from the resonant frequencies of standing Alfvén waves and the upper hybrid resonance band. The average ion mass (M) can be calculated by M ∼ ρL/neL under the assumption of quasi-neutrality of plasma. During the storm recovery phase, both Probe A and Probe B observe the oxygen torus at L = 3.0–4.0 and L = 3.7–4.5, respectively, on the morning side. The oxygen torus has M = 4.5–8 amu and extends around the plasmapause that is identified at L∼3.2–3.9. We find that during the initial phase, M is 4–7 amu throughout . . .
Date: 02/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020593 Available at: http://doi.wiley.com/10.1002/2014JA020593
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Authors: Omura Yoshiharu, Miyashita Yu, Yoshikawa Masato, Summers Danny, Hikishima Mitsuru, et al.
Title: Formation process of relativistic electron flux through interaction with chorus emissions in the Earth's inner magnetosphere
Abstract: We perform test particle simulations of energetic electrons interacting with whistler mode chorus emissions. We compute trajectories of a large number of electrons forming a delta function with the same energy and equatorial pitch angle. The electrons are launched at different locations along the magnetic field line and different timings with respect to a pair of chorus emissions generated at the magnetic equator. We follow the evolution of the delta function and obtain a distribution function in energy and equatorial pitch angle, which is a numerical Green's function for one cycle of chorus wave-particle interaction. We obtain the Green's functions for the energy range 10 keV–6 MeV and all pitch angles greater than the loss cone angle. By taking the convolution integral of the Green's f. . .
Date: 11/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 9545–9562 DOI: 10.1002/2015JA021563 Available at: http://doi.wiley.com/10.1002/2015JA021563http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021563
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Authors: Agapitov O. V., Krasnoselskikh V., Mozer F S, Artemyev A. V., and Volokitin A. S.
Title: Generation of nonlinear Electric Field Bursts in the outer radiation belt through the parametric decay of whistler waves
Abstract: Huge numbers of different non-linear structures (double layers, electron holes, non-linear whistlers, etc. referred to as Time Domain Structures - TDS) have been observed by the electric field experiment on the Van Allen Probes. Some of them are associated with whistler waves. Such TDS often emerge on the forward edges of the whistler wave packets and form chains. The parametric decay of a whistler wave into a whistler wave propagating in the opposite direction and an electron acoustic wave is studied experimentally as well as analytically, using Van Allen Probes data. The resulting electron acoustic wave is considered to be the source of electron scale TDS. The measured parameters of the three waves (two whistlers and the electron acoustic wave) are in a good agreement with an assumption . . .
Date: 05/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL064145 Available at: http://doi.wiley.com/10.1002/2015GL064145
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Authors: Motoba Tetsuo, Takahashi Kazue, Rodriguez Juan V., and Russell Christopher T.
Title: Giant pulsations on the afternoonside: Geostationary satellite and ground observations
Abstract: Giant pulsations (Pgs) are a special class of oscillations recognized in ground magnetometer records as exhibiting highly regular sinusoidal waveforms in the east-west component with periods around 100s. Previous statistical studies showed that Pgs occur almost exclusively on the morningside with peak occurrence in the postmidnight sector. In this paper, we present observations of Pgs extending to the afternoonside, using data from the GOES13 and 15 geostationary satellites and multiple ground magnetometers located in North America. For a long-lasting event on 29 February 2012, which spanned ∼08–18h magnetic local time, we show that basic Pg properties did not change with the local time, although the period of the pulsations was longer at later local time due to increasing mass loading. . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 8350 - 8367 DOI: 10.1002/2015JA021592 Available at: http://doi.wiley.com/10.1002/2015JA021592http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021592
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Authors: Shprits Y Y, and Spasojevic M.
Title: Global and comprehensive analysis of the inner magnetosphere as a coupled system: Physical understanding and applications
Abstract: The third Inner Magnetosphere Coupling (IMC III) workshop was held March 2015 at University of California, Los Angeles. The workshop included extensive discussion of space weather and applications bring together scientists from the solar wind, magnetosphere and ionospheric communities as well as space weather stakeholders and researchers focusing on translational research and applications in industry.
Date: 08/2015 Publisher: Space Weather DOI: 10.1002/2015SW001295 Available at: http://doi.wiley.com/10.1002/2015SW001295http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015SW001295
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Authors: Hwang K.-J., Sibeck D G, Fok M.-C. H., Zheng Y., Nishimura Y., et al.
Title: The global context of the 14 November, 2012 storm event
Abstract: From 2 to 5 UT on 14 November, 2012, the Van Allen Probes observed repeated particle flux dropouts during the main phase of a geomagnetic storm as the satellites traversed the post-midnight to dawnside inner magnetosphere. Each flux dropout corresponded to an abrupt change in the magnetic topology, i.e., from a more dipolar configuration to a configuration with magnetic field lines stretched in the dawn-dusk direction. Geosynchronous GOES spacecraft located in the dusk and near-midnight sectors and the LANL constellation with wide local time coverage also observed repeated flux dropouts and stretched field lines with similar occurrence patterns to those of the Van Allen Probe events. THEMIS recorded multiple transient abrupt expansions of the evening-side magnetopause ~20–30 min prior to. . .
Date: 02/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020826 Available at: http://doi.wiley.com/10.1002/2014JA020826
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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: Ukhorskiy A Y, Sitnov M I, Millan R M, Kress B T, Fennell J. F., et al.
Title: Global Storm-Time Depletion of the Outer Electron Belt
Abstract: The outer radiation belt consists of relativistic (>0.5 MeV) electrons trapped on closed trajectories around Earth where the magnetic field is nearly dipolar. During increased geomagnetic activity, electron intensities in the belt can vary by ordersof magnitude at different spatial and temporal scale. The main phase of geomagnetic storms often produces deep depletions of electron intensities over broad regions of the outer belt. Previous studies identified three possible processes that can contribute to the main-phase depletions: adiabatic inflation of electron drift orbits caused by the ring current growth, electron loss into the atmosphere, and electron escape through the magnetopause boundary. In this paper we investigate the relative importance of the adiabatic effect and magnetopause . . .
Date: 03/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020645 Available at: http://doi.wiley.com/10.1002/2014JA020645
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Authors: Breneman A. W., Halford A., Millan R., McCarthy M., Fennell J, et al.
Title: Global-scale coherence modulation of radiation-belt electron loss from plasmaspheric hiss
Abstract: Over 40 years ago it was suggested that electron loss in the region of the radiation belts that overlaps with the region of high plasma density called the plasmasphere, within four to five Earth radii1, 2, arises largely from interaction with an electromagnetic plasma wave called plasmaspheric hiss3, 4, 5. This interaction strongly influences the evolution of the radiation belts during a geomagnetic storm, and over the course of many hours to days helps to return the radiation-belt structure to its ‘quiet’ pre-storm configuration. Observations have shown that the long-term electron-loss rate is consistent with this theory but the temporal and spatial dynamics of the loss process remain to be directly verified. Here we report simultaneous measurements of structured radiation-belt electr. . .
Date: 06/2015 Publisher: Nature Pages: 193 - 195 DOI: 10.1038/nature14515 Available at: http://www.nature.com/doifinder/10.1038/nature14515
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Authors: Ferradas C. P., Zhang J.-C., Kistler L. M., and Spence H E
Title: Heavy-ion dominance near Cluster perigees
Abstract: Time periods in which heavy ions dominate over H+ in the energy range of 1-40 keV were observed by the Cluster Ion Spectrometry (CIS)/COmposition DIstribution Function (CODIF) instrument onboard Cluster Spacecraft 4 at L-values less than 4. The characteristic feature is a narrow flux peak at around 10 keV that extends into low L-values, with He+ and/or O+ dominating. In the present work we perform a statistical study of these events and examine their temporal occurrence and spatial distribution. The observed features, both the narrow energy range and the heavy-ion dominance, can be interpreted using a model of ion drift from the plasma sheet, subject to charge exchange losses. The narrow energy range corresponds to the only energy range that has direct drift access from the plasma sheet du. . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA021063 Available at: http://doi.wiley.com/10.1002/2015JA021063http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021063
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Authors: Selesnick R. S.
Title: High-energy radiation belt electrons from CRAND
Abstract: A calculation of the inner radiation belt electron source from cosmic ray albedo neutron decay (CRAND) is described. High-energy electrons are included by Lorentz-transforming the β decay spectrum from the neutron rest frame to the Earth's rest frame and combining with the known high-energy albedo neutron energy spectrum. Balancing the electron source with energy loss to atmospheric neutral atoms and plasma, and with a decay lifetime representative of plasma wave scattering, then provides an estimate of trapped electron intensity. It is well below measured values for low energies, confirming that CRAND is not a significant source of those trapped electrons. For kinetic energies above the maximum β decay energy (E > 0.8 MeV) a power law energy spectrum ∼E−4 is predicted. For L = 1.5. . .
Date: 03/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020963 Available at: http://doi.wiley.com/10.1002/2014JA020963
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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: Titova E. E., Kozelov B. V., Demekhov A. G., Manninen J., Santolik O, et al.
Title: Identification of the source of quasiperiodic VLF emissions using ground-based and Van Allen Probes satellite observations
Abstract: We report on simultaneous spacecraft and ground-based observations of quasiperiodic VLF emissions and related energetic-electron dynamics. Quasiperiodic emissions in the frequency range 2–6 kHz were observed during a substorm on 25 January 2013 by Van Allen Probe-A and a ground-based station in the Northern Finland. The spacecraft detected the VLF signals near the geomagnetic equator in the night sector at L = 3.0–4.2 when it was inside the plasmasphere. During the satellite motion toward higher latitudes, the time interval between quasiperiodic elements decreased from 6 min to 3 min. We find one-to-one correspondence between the quasiperiodic elements detected by Van Allen Probe-A and on the ground, which indicates the temporal nature of the observed variation in the time in. . .
Date: 08/2015 Publisher: Geophysical Research Letters Pages: 6137 - 6145 DOI: 10.1002/grl.v42.1510.1002/2015GL064911 Available at: http://doi.wiley.com/10.1002/2015GL064911
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Authors: Zhou Xu-Zhi, Wang Zi-Han, Zong Qiu-Gang, Claudepierre Seth G., Mann Ian R., et al.
Title: Imprints of impulse-excited hydromagnetic waves on electrons in the Van Allen radiation belts
Abstract: Ultralow frequency electromagnetic oscillations, interpreted as standing hydromagnetic waves in the magnetosphere, are a major energy source that accelerates electrons to relativistic energies in the Van Allen radiation belt. Electrons can rapidly gain energy from the waves when they resonate via a process called drift resonance, which is observationally characterized by energy-dependent phase differences between electron flux and electromagnetic oscillations. Such dependence has been recently observed and interpreted as spacecraft identifications of drift resonance electron acceleration. Here we show that in the initial wave cycles, the observed phase relationship differs from that characteristic of well-developed drift resonance. We further examine the differences and find that they are . . .
Date: 08/2015 Publisher: Geophysical Research Letters Pages: 6199 - 6204 DOI: 10.1002/grl.v42.1510.1002/2015GL064988 Available at: http://doi.wiley.com/10.1002/grl.v42.15http://doi.wiley.com/10.1002/2015GL064988
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Authors: Yu Xiongdong, Yuan Zhigang, Wang Dedong, Li Haimeng, Huang Shiyong, et al.
Title: In situ observations of EMIC waves in O + band by the Van Allen Probe A
Abstract: Through polarization and spectra analysis of the magnetic field observed by the Van Allen Probe A, we present two typical cases of O+ band EMIC waves in the outer plasmasphere or plasma trough. Although such O+ band EMIC waves are rarely observed, 18 different events of O+ band EMIC waves (16 events in the outer plasmasphere and 2 events in the plasma trough) are found from September 2012 to August 2014 with observations of the Van Allen Probe A. We find that the preferred region for the occurrence of O+ band EMIC waves is in L = 2-5 and MLT = 03-13, 19-20, which is in accordance with the occurrence region of O+ ion torus. Therefore, our result suggests that the O+ ion torus in the outer plasmasphere during geomagnetic activities should play an important role in the generation of EMIC wave. . .
Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL063250 Available at: http://doi.wiley.com/10.1002/2015GL063250
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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: Němec F., Santolik O, Hrbáčková Z., and Cornilleau-Wehrlin N.
Title: Intensities and spatiotemporal variability of equatorial noise emissions observed by the Cluster spacecraft
Abstract: Equatorial noise (EN) emissions are electromagnetic waves observed in the equatorial region of the inner magnetosphere at frequencies between the proton cyclotron frequency and the lower hybrid frequency. We present the analysis of 2229 EN events identified in the Spatio-Temporal Analysis of Field Fluctuations (STAFF) experiment data of the Cluster spacecraft during the years 2001–2010. EN emissions are distinguished using the polarization analysis, and their intensity is determined based on the evaluation of the Poynting flux rather than on the evaluation of only the electric/magnetic field intensity. The intensity of EN events is analyzed as a function of the frequency, the position of the spacecraft inside/outside the plasmasphere, magnetic local time, and the geomagnetic activity. Th. . .
Date: 03/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 1620 - 1632 DOI: 10.1002/2014JA020814 Available at: http://doi.wiley.com/10.1002/2014JA020814
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Authors: Skov Tamitha Mulligan, Fennell Joseph F., Roeder James L., Blake Bernard, and Claudepierre Seth G.
Title: Internal Charging Hazards in Near-Earth Space During Solar Cycle 24 Maximum: Van Allen Probes Measurements
Abstract: The Van Allen Probes mission provides an unprecedented opportunity to make detailed measurements of electrons and protons in the inner magnetosphere during the weak solar maximum period of cycle 24. The MagEIS suite of sensors measures energy spectra and fluxes of charged particles in the space environment. The calculations show that these fluxes result in electron deposition rates high enough to cause internal charging. We use omnidirectional fluxes of electrons and protons to calculate the dose under varying materials and thicknesses of shielding. We show examples of charge deposition rates during the times of nominal and high levels of penetrating fluxes in the inner magnetosphere covering the period from the beginning of 2013 through mid-2014. These charge deposition rates are related . . .
Date: 09/2015 Publisher: IEEE Transactions on Plasma Science Pages: 3070 - 3074 DOI: 10.1109/TPS.2015.2468214 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=7247811http://xplorestaging.ieee.org/ielx7/27/7247791/07247811.pdf?arnumber=7247811
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Authors: Skov Mulligan, Fennell J.F., Roeder J.L., Blake J.B., and Claudepierre S.G.
Title: Internal Charging Hazards in Near-Earth Space during Solar Cycle 24 Maximum: Van Allen Probes Measurements
Abstract: The Van Allen Probes mission provides an unprecedented opportunity to make detailed measurements of electrons and protons in the inner magnetosphere during the weak solar maximum period of cycle 24. Data from the MagEIS suite of sensors measures energy spectra, fluxes, and yields electron deposition rates that can cause internal charging. We use omni-directional fluxes of electrons and protons to calculate the dose under varying materials and thicknesses of shielding (similar to Fennell et al., 2010). We show examples of charge deposition rates during times of nominal and high levels of penetrating fluxes in the inner magnetosphere covering the period from late 2012 through 2013. These charge deposition rates are related to charging levels quite possibly encountered. . .
Date: 09/2015 Publisher: JPL DOI: 10.1109/TPS.2015.2468214 Available at: http://ieeexplore.ieee.org/document/7247811/?reload=true&arnumber=7247811
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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: Tejero E. M., Crabtree C., Blackwell D. D., Amatucci W. E., Mithaiwala M., et al.
Title: Laboratory studies of nonlinear whistler wave processes in the Van Allen radiation belts
Abstract: Important nonlinear wave-wave and wave-particle interactions that occur in the Earth's Van Allen radiation belts are investigated in a laboratory experiment. Predominantly electrostatic waves in the whistler branch are launched that propagate near the resonance cone with measured wave normal angle greater than 85° . When the pump amplitude exceeds a threshold ∼5×10−6 times the background magnetic field, wave power at frequencies below the pump frequency is observed at wave normal angles (∼55°) . The scattered wave has a perpendicular wavelength that is nearly an order of magnitude larger than that of the pump wave. Occasionally, the parametric decay of a lower hybrid wave into a magnetosonic wave and a whistler wave is simultaneously observed with a threshold of δB/B0∼7×10−7. . .
Date: 09/2015 Publisher: Physics of Plasmas Pages: 091503 DOI: 10.1063/1.4928944 Available at: http://scitation.aip.org/content/aip/journal/pop/22/9/10.1063/1.4928944
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Authors: Tejero E. M., Crabtree C., Blackwell D. D., Amatucci W. E., Mithaiwala M., et al.
Title: Laboratory studies of nonlinear whistler wave processes in the Van Allen radiation belts
Abstract: Important nonlinear wave-wave and wave-particle interactions that occur in the Earth’s Van Allen radiation belts are investigated in a laboratory experiment. Predominantly electrostatic waves in the whistler branch are launched that propagate near the resonance cone with measured wave normal angle greater than 85º. When the pump amplitude exceeds a threshold ~5 x10^6 times the back- ground magnetic field, wave power at frequencies below the pump frequency is observed at wave normal angles (~55º). The scattered wave has a perpendicular wavelength that is nearly an order of magnitude larger than that of the pump wave. Occasionally, the parametric decay of a lower hybrid wave into a magnetosonic wave and a whistler wave is simultaneously observed with a threshold of δB=B_0 ~7 x 10^-7. . .
Date: 08/2015 Publisher: Physics of Plasmas DOI: 10.1063/1.4928944 Available at: http://scitation.aip.org/content/aip/journal/pop/22/9/10.1063/1.4928944
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Authors: Motoba T., Takahashi K., Ukhorskiy A., Gkioulidou M., Mitchell D G, et al.
Title: Link between pre-midnight second harmonic poloidal waves and auroral undulations: Conjugate observations with a Van Allen Probes spacecraft and a THEMIS all-sky imager
Abstract: We report, for the first time, an auroral undulation event on 1 May 2013 observed by an all-sky imager (ASI) at Athabasca (L = 4.6), Canada, for which in situ field and particle measurements in the conjugate magnetosphere were available from a Van Allen Probes spacecraft. The ASI observed a train of auroral undulation structures emerging spontaneously in the pre-midnight subauroral ionosphere, during the growth phase of a substorm. The undulations had an azimuthal wavelength of ~180 km and propagated westward at a speed of 3–4 km s−1. The successive passage over an observing point yielded quasi-periodic oscillations in diffuse auroral emissions with a period of ~40 s. The azimuthal wave number m of the auroral luminosity oscillations was found to be m ~ −103. During the event the spa. . .
Date: 02/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020863 Available at: http://doi.wiley.com/10.1002/2014JA020863
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Authors: Shue Jih-Hong, Hsieh Yi-Kai, Tam Sunny W. Y., Wang Kaiti, Fu Hui Shan, et al.
Title: Local time distributions of repetition periods for rising tone lower band chorus waves in the magnetosphere
Abstract: Whistler mode chorus waves generally occur outside the plasmapause in the magnetosphere. The most striking feature of the waves is their occurrence in discrete elements. One of the parameters that describe the discrete elements is the repetition period (Trp), the time between consecutive elements. The Trp has not been studied statistically before. We use high-resolution waveform data to derive distributions of Trp for different local times. We find that the average Trp for the nightside (0.56 s) and dawnside (0.53 s) are smaller than those for the dayside (0.81 s) and duskside (0.97 s). Through a comparison with the background plasma and magnetic fields, we also find that the total magnetic field and temperature are the main controlling factors that affect the variability of Trp. These res. . .
Date: 10/2015 Publisher: Geophysical Research Letters Pages: 8294 - 8301 DOI: 10.1002/2015GL066107 Available at: http://doi.wiley.com/10.1002/2015GL066107http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015GL066107
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Authors: Neal Jason J., Rodger Craig J., Clilverd Mark A., Thomson Neil R., Raita Tero, et al.
Title: Long-term determination of energetic electron precipitation into the atmosphere from AARDDVARK subionospheric VLF observations
Abstract: We analyze observations of subionospherically propagating very low frequency (VLF) radio waves to determine outer radiation belt energetic electron precipitation (EEP) flux magnitudes. The radio wave receiver in Sodankylä, Finland (Sodankylä Geophysical Observatory) observes signals from the transmitter with call sign NAA (Cutler, Maine). The receiver is part of the Antarctic-Arctic Radiation-belt Dynamic Deposition VLF Atmospheric Research Konsortia (AARDDVARK). We use a near-continuous data set spanning November 2004 until December 2013 to determine the long time period EEP variations. We determine quiet day curves over the entire period and use these to identify propagation disturbances caused by EEP. Long Wave Propagation Code radio wave propagation modeling is used to estimate the p. . .
Date: 03/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020689 Available at: http://doi.wiley.com/10.1002/2014JA020689
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Authors: Posch J. L, Engebretson M. J., Olson C. N., Thaller S. A., Breneman A. W., et al.
Title: Low-harmonic magnetosonic waves observed by the Van Allen Probes
Abstract: Purely compressional electromagnetic waves (fast magnetosonic waves), generated at multiple harmonics of the local proton gyrofrequency, have been observed by various types of satellite instruments (fluxgate and search coil magnetometers and electric field sensors), but most recent studies have used data from search coil sensors, and many have been restricted to high harmonics. We report here on a survey of low-harmonic waves, based on electric and magnetic field data from the EFW double probe and EMFISIS fluxgate magnetometer instruments, respectively, on the Van Allen Probes spacecraft during its first full precession through all local times, from October 1, 2012 through July 13, 2014. These waves were observed both inside and outside the plasmapause (PP), at L shells from 2.4 to ~6 (the. . .
Date: 07/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021179 Available at: http://doi.wiley.com/10.1002/2015JA021179
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Authors: Vasko I. Y., Agapitov O. V., Mozer F, Artemyev A. V., and Jovanovic D.
Title: Magnetic field depression within electron holes
Abstract: We analyze electron holes that are spikes of the electrostatic field (up to 500 mV/m) observed by Van Allen Probes in the outer radiation belt. The unexpected feature is the magnetic field depression of about several tens of picotesla within many of the spikes. The earlier observations showed amplification or negligible perturbations of the magnetic field within the electron holes. We suggest that the observed magnetic field depression is due to the diamagnetic current of hot and highly anisotropic population of electrons trapped within the electron holes. The required trapped population should have a density up to 65% of the background plasma density, a temperature up to several keV, and a temperature anisotropy T⊥/T∥∼2. We argue that the observed electron holes could be generated. . .
Date: 04/2015 Publisher: Geophysical Research Letters Pages: 2123 - 2129 DOI: 10.1002/2015GL063370 Available at: http://doi.wiley.com/10.1002/2015GL063370
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Authors: Ali Ashar F., Elkington Scot R, Tu Weichao, Ozeke Louis G., Chan Anthony A, et al.
Title: Magnetic field power spectra and magnetic radial diffusion coefficients using CRRES magnetometer data
Abstract: We used the fluxgate magnetometer data from Combined Release and Radiation Effects Satellite (CRRES) to estimate the power spectral density (PSD) of the compressional component of the geomagnetic field in the ∼1 mHz to ∼8 mHz range. We conclude that magnetic wave power is generally higher in the noon sector for quiet times with no significant difference between the dawn, dusk, and the midnight sectors. However, during high Kp activity, the noon sector is not necessarily dominant anymore. The magnetic PSDs have a very distinct dependence on Kp. In addition, the PSDs appear to have a weak dependence on McIlwain parameter L with power slightly increasing as L increases. The magnetic wave PSDs are used along with the Fei et al. (2006) formulation to compute inline image as a function of L . . .
Date: 02/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020419 Available at: http://doi.wiley.com/10.1002/2014JA020419
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Authors: Paral J., Hudson M K, Kress B T, Wiltberger M. J., Wygant J R, et al.
Title: Magnetohydrodynamic modeling of three Van Allen Probes storms in 2012 and 2013
Abstract: Coronal mass ejection (CME)-shock compression of the dayside magnetopause has been observed to cause both prompt enhancement of radiation belt electron flux due to inward radial transport of electrons conserving their first adiabatic invariant and prompt losses which at times entirely eliminate the outer zone. Recent numerical studies suggest that enhanced ultra-low frequency (ULF) wave activity is necessary to explain electron losses deeper inside the magnetosphere than magnetopause incursion following CME-shock arrival. A combination of radial transport and magnetopause shadowing can account for losses observed at radial distances into L = 4.5, well within the computed magnetopause location. We compare ULF wave power from the Electric Field and Waves (EFW) electric field instrument on th. . .
Date: 08/2015 Publisher: Annales Geophysicae Pages: 1037 - 1050 DOI: 10.5194/angeo-33-1037-2015 Available at: http://www.ann-geophys.net/33/1037/2015/angeo-33-1037-2015.pdf
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Authors: Selesnick R. S.
Title: Measurement of inner radiation belt electrons with kinetic energy above 1 MeV
Abstract: Data from the Proton-Electron Telescope on the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite, taken during 1992–2009, are analyzed for evidence of inner radiation belt electrons with kinetic energy E > 1 MeV. It is found that most of the data from a detector combination with a nominal energy threshold of 1 MeV were, in fact, caused by a chance coincidence response to lower energy electrons or high-energy protons. In particular, there was no detection of inner belt or slot region electrons above 1 MeV following the 2003 Halloween storm injection, though they may have been present. However, by restricting data to a less-stable, low-altitude trapping region, a persistent presence of inner belt electrons in the energy range 1 to 1.6 MeV is demonstrated. Their soft. . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 8339 - 8349 DOI: 10.1002/2015JA021387 Available at: http://doi.wiley.com/10.1002/2015JA021387http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021387
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Authors: Hudson M K, Paral J., Kress B T, Wiltberger M., Baker D N, et al.
Title: Modeling CME-shock driven storms in 2012 - 2013: MHD-test particle simulations
Abstract: The Van Allen Probes spacecraft have provided detailed observations of the energetic particles and fields environment for CME-shock driven storms in 2012 to 2013 which have now been modeled with MHD-test particle simulations. The Van Allen Probes orbital plane longitude moved from the dawn sector in 2012 to near midnight and pre-noon for equinoctial storms of 2013, providing particularly good measurements of the inductive electric field response to magnetopause compression for the 8 October 2013 CME-shock driven storm. An abrupt decrease in the outer boundary of outer zone electrons coincided with inward motion of the magnetopause for both 17 March and 8 October 2013 storms, as was the case for storms shortly after launch (Hudson et al., 2014). Modeling magnetopause dropout events in 2013 . . .
Date: 01/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020833 Available at: http://doi.wiley.com/10.1002/2014JA020833
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Authors: Ma Q, Li W, Thorne R M, Ni B, Kletzing C A, et al.
Title: Modeling inward diffusion and slow decay of energetic electrons in the Earth's outer radiation belt
Abstract: A new 3D diffusion code is used to investigate the inward intrusion and slow decay of energetic radiation belt electrons (>0.5 MeV) observed by the Van Allen Probes during a 10-day quiet period in March 2013. During the inward transport the peak differential electron fluxes decreased by approximately an order of magnitude at various energies. Our 3D radiation belt simulation including radial diffusion and pitch angle and energy diffusion by plasmaspheric hiss and Electromagnetic Ion Cyclotron (EMIC) waves reproduces the essential features of the observed electron flux evolution. The decay timescales and the pitch angle distributions in our simulation are consistent with the Van Allen Probes observations over multiple energy channels. Our study suggests that the quiet-time energetic electro. . .
Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062977 Available at: http://doi.wiley.com/10.1002/2014GL062977
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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: 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: Dixon P., MacDonald E A, Funsten H O, Glocer A., Grande M., et al.
Title: Multipoint observations of the open-closed field line boundary as observed by the Van Allen Probes and geostationary satellites during the November 14 th 2012 geomagnetic storm
Abstract: The twin Van Allen Probes spacecraft witnessed a series of lobe encounters between 0200 and 0515 UT on November 14th 2012. Although lobe entry had been observed previously by the other spacecraft, the two Van Allen Probe spacecraft allow us to observe the motion of the boundary for the first time. Moreover, this event is unique in that it consists of a series of six quasi-periodic lobe entries. The events occurred on the dawn flank between 4 and 6.6 local time and at altitudes between 5.6 and 6.2 RE. During the events Dst dropped to less than -100nT with the IMF being strongly southward (Bz = −15nT) and eastward (By = 20 nT). Observations by LANL GEO spacecraft at geosynchronous orbit also show lobe encounters in the northern hemisphere and on the dusk flank. The two spacecraf. . .
Date: 05/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020883 Available at: http://doi.wiley.com/10.1002/2014JA020883
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Authors: Dai Lei, Wang Chi, Duan Suping, He Zhaohai, Wygant John R., et al.
Title: Near-Earth Injection of MeV Electrons associated with Intense Dipolarization Electric Fields: Van Allen Probes observations
Abstract: Substorms generally inject 10s-100s keV electrons, but intense substorm electric fields have been shown to inject MeV electrons as well. An intriguing question is whether such MeV electron injections can populate the outer radiation belt. Here we present observations of a substorm injection of MeV electrons into the inner magnetosphere. In the pre-midnight sector at L∼5.5, Van Allen Probes (RBSP)-A observed a large dipolarization electric field (50mV/m) over ∼40s and a dispersionless injection of electrons up to ∼3 MeV. Pitch angle observations indicated betatron acceleration of MeV electrons at the dipolarization front. Corresponding signals of MeV electron injection were observed at LANL-GEO, THEMIS-D, and GOES at geosynchronous altitude. Through a series of dipolarizations, the in. . .
Date: 07/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL064955 Available at: http://doi.wiley.com/10.1002/2015GL064955
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Authors: Bonnell John, and Lanzerotti Louis J.
Title: Neutral Oxygen Effects at Low Earth Altitudes: A Critical Uncertainty for Spacecraft Operations and Space Weather Effects
Abstract: Space Weather sits at the intersection of natural phenomena interacting with modern technology—either in space or on Earth's surface. A key aspect of space weather is the interaction of Earth's extended neutral atmosphere with satellite surfaces [e.g., Samwel, 2014, and references therein]. Because neutral oxygen causes spacecraft surface erosion and oxidation, detailed knowledge of the atmosphere below 1000 km is essential for spacecraft design and operations.
Date: 07/2015 Publisher: Space Weather DOI: 10.1002/2015SW001229 Available at: http://doi.wiley.com/10.1002/2015SW001229
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