Found 21 results
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Authors: Jaynes A. N., Ali A. F., Elkington S R, Malaspina D. M., Baker D N, et al.
Title: Fast diffusion of ultra-relativistic electrons in the outer radiation belt: 17 March 2015 storm event
Abstract: Inward radial diffusion driven by ULF waves has long been known to be capable of accelerating radiation belt electrons to very high energies within the heart of the belts, but more recent work has shown that radial diffusion values can be highly event‐specific and mean values or empirical models may not capture the full significance of radial diffusion to acceleration events. Here we present an event of fast inward radial diffusion, occurring during a period following the geomagnetic storm of 17 March 2015. Ultra‐relativistic electrons up to ∼8 MeV are accelerated in the absence of intense higher‐frequency plasma waves, indicating an acceleration event in the core of the outer belt driven primarily or entirely by ULF wave‐driven diffusion. We examine this fast diffusion rate alon. . .
Date: 09/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079786 Available at:
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Authors: Min Kyungguk, Liu Kaijun, Wang Xueyi, Chen Lunjin, and Denton Richard E
Title: Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism
Abstract: Linear Vlasov theory and particle-in-cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Ωp and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, ∂fp/∂v⊥>0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to hav. . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024867 Available at:
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Authors: Nakamura S., Omura Y., and Summers D.
Title: Fine structure of whistler-mode hiss in plasmaspheric plumes observed by the Van Allen Probes
Abstract: We survey 3 years (2013‐2015) of data from the Van Allen Probes related to plasmaspheric plume crossing events. We detect 194 plume crossing events, and we find that 97% of the plumes are accompanied by VLF hiss emissions. The plumes are mainly detected on the duskside or dayside. Careful examination of the hiss spectra reveals that all hiss emissions consist of obvious fine structure. Application of a band pass filter reveals that the fine structure is consistent with the occurrence of discrete wave packets. The hiss data display high coherency. The events are classified by location. Dusk side hiss and night side hiss tend to have extremely high polarization with no chorus at the high‐frequency end of the dynamic spectrum. The dusk side hiss has a distinct upper frequency limit. On th. . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025803 Available at:
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Authors: Maurer R H, Goldsten J O, Butler M. H., and Fretz K.
Title: Five Year Results from the Engineering Radiation Monitor (ERM) and Solar Cell Monitor on the Van Allen Probes Mission
Abstract: The Engineering Radiation Monitor (ERM) measures dose, dose rate and charging currents on the Van Allen Probes mission to study the dynamics of Earth's Van Allen radiation belts. Over five years, results from this monitor show a variation in dose rates with time, a correlation between the dosimeter and charging current data and a comparison of cumulative dose to pre‐launch modeling. Solar cell degradation monitor patches track the decrease in solar array output as displacement damage accumulates. The Solar Cell Monitor shows ~33% cumulative degradation in maximum power after 5.1 years of the mission. The desire to extend the mission to ~2500 days from 800 days created increased requirements for the ionizing radiation hardness of spacecraft and science instrument electronics. We describe . . .
Date: 09/2018 Publisher: Space Weather DOI: 10.1029/2018SW001910 Available at:
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Authors: Ozaki M., Shiokawa K., Miyoshi Y, Kataoka R., Yagitani S., et al.
Title: Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes
Abstract: To understand the role of electromagnetic ion cyclotron (EMIC) waves in determining the temporal features of pulsating proton aurora (PPA) via wave-particle interactions at subauroral latitudes, high-time-resolution (1/8 s) images of proton-induced N2+ emissions were recorded using a new electron multiplying charge-coupled device camera, along with related Pc1 pulsations on the ground. The observed Pc1 pulsations consisted of successive rising-tone elements with a spacing for each element of 100 s and subpacket structures, which manifest as amplitude modulations with a period of a few tens of seconds. In accordance with the temporal features of the Pc1 pulsations, the auroral intensity showed a similar repetition period of 100 s and an unpredicted fast modulation of a few tens of sec. . .
Date: 08/2016 Publisher: Geophysical Research Letters Pages: 7859 - 7866 DOI: 10.1002/2016GL070008 Available at:
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Authors: Chen Yue, Reeves Geoffrey D, Cunningham Gregory S., Redmon Robert J., and Henderson Michael G.
Title: Forecasting and remote sensing outer belt relativistic electrons from low Earth orbit
Abstract: This study demonstrates the feasibility and reliability of using observations from low Earth orbit (LEO) to forecast and nowcast relativistic electrons in the outer radiation belt. We first report a high cross-energy, cross-pitch-angle coherence discovered between the trapped MeV electrons and precipitating approximately hundreds (~100s) of keV electrons—observed by satellites with very different altitudes—with correlation coefficients as high as ≳ 0.85. Based upon the coherence, we then tested the feasibility of applying linear prediction filters to LEO data to predict the arrival of new MeV electrons during geomagnetic storms, as well as their evolving distributions afterward. Reliability of these predictive filters is quantified by the performance efficiency with values as high . . .
Date: 02/2016 Publisher: Geophysical Research Letters Pages: 1031 - 1038 DOI: 10.1002/2015GL067481 Available at:
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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:
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Authors: Su Yi-Jiun, Selesnick Richard S., and Blake J B
Title: Formation of the inner electron radiation belt by enhanced large-scale electric fields
Abstract: A two-dimensional bounce-averaged test particle code was developed to examine trapped electron trajectories during geomagnetic storms with the assumption of conservation of the first and second adiabatic invariants. The March 2013 storm was selected as an example because the geomagnetic activity Kp index sharply increased from 2 + to 7− at 6:00 UT on 17 March. Electron measurements with energies between 37 and 460 keV from the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard Van Allen Probes (VAP) are used as initial conditions prior to the storm onset and served to validate test particle simulations during the storm. Simulation results help to interpret the observed electron injection as nondiffusive radial transport over a short distance in the inner belt and slot. . .
Date: 08/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022881 Available at:
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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:
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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:
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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:
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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:
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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:
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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:
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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:
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Authors: Artemyev A. V., Vasiliev A. A., Mourenas D., Agapitov O. V., Krasnoselskikh V., et al.
Title: Fast transport of resonant electrons in phase space due to nonlinear trapping by whistler waves
Abstract: We present an analytical, simplified formulation accounting for the fast transport of relativistic electrons in phase space due to wave-particle resonant interactions in the inhomogeneous magnetic field of Earth's radiation belts. We show that the usual description of the evolution of the particle velocity distribution based on the Fokker-Planck equation can be modified to incorporate nonlinear processes of wave-particle interaction, including particle trapping. Such a modification consists in one additional operator describing fast particle jumps in phase space. The proposed, general approach is used to describe the acceleration of relativistic electrons by oblique whistler waves in the radiation belts. We demonstrate that for a wave power distribution with a hard enough power law tail in. . .
Date: 08/2014 Publisher: Geophysical Research Letters Pages: 5727 - 5733 DOI: 10.1002/grl.v41.1610.1002/2014GL061380 Available at:
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Authors: McKenna-Lawlor Susan
Title: Feasibility study of astronaut standardized career dose limits in LEO and the outlook for BLEO
Abstract: Cosmic Study Group SG 3.19/1.10 was established in February 2013 under the aegis of the International Academy of Astronautics to consider and compare the dose limits adopted by various space agencies for astronauts in Low Earth Orbit. A preliminary definition of the limits that might later be adopted by crews exploring Beyond Low Earth Orbit was, in addition, to be made. The present paper presents preliminary results of the study reported at a Symposium held in Turin by the Academy in July 2013. First, an account is provided of exposure limits assigned by various partner space agencies to those of their astronauts that work aboard the International Space Station. Then, gaps in the scientific and technical information required to safely implement human missions beyond the shielding provided. . .
Date: 11/2014 Publisher: Acta Astronautica Pages: 565 - 573 DOI: 10.1016/j.actaastro.2014.07.011 Available at:
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Authors: Santolik O, Kletzing C A, Kurth W S, Hospodarsky G B, and Bounds S R
Title: Fine structure of large-amplitude chorus wave packets
Abstract: Whistler mode chorus waves in the outer Van Allen belt can have consequences for acceleration of relativistic electrons through wave-particle interactions. New multicomponent waveform measurements have been collected by the Van Allen Probes Electric and Magnetic Field Instrument Suite and Integrated Science's Waves instrument. We detect fine structure of chorus elements with peak instantaneous amplitudes of a few hundred picotesla but exceptionally reaching up to 3 nT, i.e., more than 1% of the background magnetic field. The wave vector direction turns by a few tens of degrees within a single chorus element but also within its subpackets. Our analysis of a significant number of subpackets embedded in rising frequency elements shows that amplitudes of their peaks tend to decrease with frequ. . .
Date: 01/2014 Publisher: Geophysical Research Letters Pages: 293 - 299 DOI: 10.1002/2013GL058889 Available at:
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Authors: Summers Danny, Omura Yoshiharu, Nakamura Satoko, and Kletzing Craig A.
Title: Fine structure of plasmaspheric hiss
Abstract: Plasmaspheric hiss has been widely regarded as a broadband, structureless, incoherent emission. In this study, by examining burst-mode vector waveform data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument on the Van Allen Probes mission, we show that plasmaspheric hiss is a coherent emission with complex fine structure. Specifically, plasmaspheric hiss appears as discrete rising tone and falling tone elements. Our study comprises the analysis of two one-hour samples within which a total of 8 one-second samples were analyzed. By means of waveform analysis on two samples we identify typical amplitudes, phase profiles, and sweep rates of the rising and falling tone elements. The exciting new observations reported here can be expected to fuel a . . .
Date: 12/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020437 Available at:
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Authors: Fu H. S., Cao J. B., Zhima Z., Khotyaintsev Y. V., Angelopoulos V, et al.
Title: First observation of rising-tone magnetosonic waves
Abstract: Magnetosonic (MS) waves are linearly polarized emissions confined near the magnetic equator with wave normal angle near 90° and frequency below the lower hybrid frequency. Such waves, also termed equatorial noise, were traditionally known to be “temporally continuous” in their time-frequency spectrogram. Here we show for the first time that MS waves actually have discrete wave elements with rising-tone features in their spectrogram. The frequency sweep rate of MS waves, ~1 Hz/s, is between that of chorus and electromagnetic ion cyclotron (EMIC) waves. For the two events we analyzed, MS waves occur outside the plasmapause and cannot penetrate into the plasmasphere; their power is smaller than that of chorus. We suggest that the rising-tone feature of MS waves is a consequence of nonl. . .
Date: 11/2014 Publisher: Geophysical Research Letters Pages: 7419 - 7426 DOI: 10.1002/grl.v41.2110.1002/2014GL061867 Available at:
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Authors: Li X, Schiller Q., Blum L., Califf S., Zhao H., et al.
Title: First Results from CSSWE CubeSat: Characteristics of Relativistic Electrons in the Near-Earth Environment During the October 2012 Magnetic Storms
Abstract: Measurements from the Relativistic Electron and Proton Telescope integrated little experiment (REPTile) on board the Colorado Student Space Weather Experiment (CSSWE) CubeSat mission, which was launched into a highly inclined (65°) low Earth orbit, are analyzed along with measurements from the Relativistic Electron and Proton Telescope (REPT) and the Magnetic Electron Ion Spectrometer (MagEIS) instruments aboard the Van Allen Probes, which are in a low inclination (10°) geo-transfer-like orbit. Both REPT and MagEIS measure the full distribution of energetic electrons as they traverse the heart of the outer radiation belt. However, due to the small equatorial loss cone (only a few degrees), it is difficult for REPT and MagEIS to directly determine which electrons will precipitate into the. . .
Date: 10/2013 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2013JA019342 Available at:
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