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Found 608 results

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2014
Authors: Menietti J. D., Averkamp T. F., Groene J. B., Horne R B, Shprits Y Y, et al.
Title: Survey analysis of chorus intensity at Saturn
Abstract: In order to conduct theoretical studies or modeling of pitch angle scattering of electrons by whistler mode chorus emission at Saturn, a knowledge of chorus occurrence and magnetic intensity levels, PB, as well as the distribution of PB relative to frequency and spatial parameters is essential. In this paper an extensive survey of whistler mode magnetic intensity levels at Saturn is carried out, and Gaussian fits of PB are performed. We fit the spectrum of wave magnetic intensity between the lower hybrid frequency and fceq/2 and for frequencies in the interval fceq/2 < f < 0.9 fceq, where fceq is the cyclotron frequency mapped to the equator. Saturn chorus is observed over most local times, but is dominant on the nightside in the range of 4.5 < L <7.5, with minimum power at t. . .
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 8415 - 8425 DOI: 10.1002/jgra.v119.1010.1002/2014JA020523 Available at: http://doi.wiley.com/10.1002/jgra.v119.10http://doi.wiley.com/10.1002/2014JA020523
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Authors: Califf S., Li X, Blum L., Jaynes A., Schiller Q., et al.
Title: THEMIS measurements of quasi-static electric fields in the inner magnetosphere
Abstract: We use four years of THEMIS double-probe measurements to offer, for the first time, a complete picture of the dawn-dusk electric field covering all local times and radial distances in the inner magnetosphere based on in situ equatorial observations. This study is motivated by the results from the CRRES mission, which revealed a local maximum in the electric field developing near Earth during storm times, rather than the expected enhancement at higher L shells that is shielded near Earth as suggested by the Volland-Stern model. The CRRES observations were limited to the dusk side, while THEMIS provides complete local time coverage. We show strong agreement with the CRRES results on the dusk side, with a local maximum near L =4 for moderate levels of geomagnetic activity and evidence of stro. . .
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020360 Available at: http://doi.wiley.com/10.1002/2014JA020360
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Authors: Osmane A., and Pulkkinen T. I.
Title: On the threshold energization of radiation belt electrons by double layers
Abstract: Using a Hamiltonian approach, we quantify the energization threshold of electrons interacting with radiation belts' double layers discovered by Mozer et al. (2013). We find that double layers with electric field amplitude E0 ranging between 10 and 100 mV/m and spatial scales of the order of few Debye lengths are very efficient in energizing electrons with initial velocities v∥ ≤ vth to 1 keV levels but are unable to energize electrons with E ≥ 100 keV. Our results indicate that the localized electric field associated with the double layers are unlikely to generate a seed population of 100 keV necessary for a plethora of relativistic acceleration mechanisms and additional transport to higher energetic levels.
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020236 Available at: http://doi.wiley.com/10.1002/2014JA020236
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Authors: Murphy Kyle R., Mann Ian R., and Ozeke Louis G.
Title: A ULF wave driver of ring current energization
Abstract: ULF wave radial diffusion plays an important role in the transport of energetic electrons in the outer radiation belt, yet similar ring current transport is seldom considered even though ions satisfy a nearly identical drift resonance condition albeit without the relativistic correction. By examining the correlation between ULF wave power and the response of the ring current, characterized by Dst, we demonstrate a definite correlation between ULF wave power and Dst. Significantly, the lagged correlation peaks such that ULF waves precede the response of the ring current and Dst. We suggest that this correlation is the result of enhanced radial transport and energization of ring current ions through drift resonance and ULF wave radial diffusion of ring current ions. An analysis and compariso. . .
Date: 10/2014 Publisher: Geophysical Research Letters Pages: 6595 - 6602 DOI: 10.1002/grl.v41.1910.1002/2014GL061253 Available at: http://doi.wiley.com/10.1002/grl.v41.19http://doi.wiley.com/10.1002/2014GL061253
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Authors: Yang Xiao C., Zhu Guang W., Zhang Xiao X., Sun Yue Q., Liang Jin B., et al.
Title: An unusual long-lived relativistic electron enhancement event excited by sequential CMEs
Abstract: An unusual long-lived intense relativistic electron enhancement event from July to August 2004 is examined using data from Fengyun-1, POES, GOES, ACE, the Cluster Mission and geomagnetic indices. During the initial 6 days of this event, the observed fluxes in the outer zone enhanced continuously and their maximum increased from 2.1 × 102 cm-2·sr-1·s-1 to 3.5 × 104 cm-2·sr-1·s-1, the region of enhanced fluxes extended from L = 3.5-6.5 to L = 2.5-6.5, and the flux peak location shifted inward from L ~ 4.2 to L ~ 3.3. During the following 7 days, without any locational movement, the flux peak increased slowly and exceeded the pre-storm fluxes by about 4 orders of magnitude. Subsequently, the decay rate of relativistic electrons is so slow that the peak re. . .
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA019797 Available at: http://doi.wiley.com/10.1002/2014JA019797
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Authors: Fu Xiangrong, Cowee Misa M., Friedel Reinhard H., Funsten Herbert O, Gary Peter, et al.
Title: Whistler Anisotropy Instabilities as the Source of Banded Chorus: Van Allen Probes Observations and Particle-in-Cell Simulations
Abstract: Magnetospheric banded chorus is enhanced whistler waves with frequencies ωr < Ωe, where Ωe is the electron cyclotron frequency, and a characteristic spectral gap at ωr ≃ Ωe/2. This paper uses spacecraft observations and two-dimensional particle-in-cell (PIC) simulations in a magnetized, homogeneous, collisionless plasma to test the hypothesis that banded chorus is due to local linear growth of two branches of the whistler anisotropy instability excited by two distinct, anisotropic electron components of significantly different temperatures. The electron densities and temperatures are derived from HOPE instrument measurements on the Van Allen Probes A satellite during a banded chorus event on 1 November 2012. The observations are consistent with a three-component electron mod. . .
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020364 Available at: http://doi.wiley.com/10.1002/2014JA020364
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Authors: Fok M.-C., Buzulukova N. Y., Chen S.-H., Glocer A., Nagai T., et al.
Title: The Comprehensive Inner Magnetosphere-Ionosphere Model
Abstract: Simulation studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the r. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7522 - 7540 DOI: 10.1002/jgra.v119.910.1002/2014JA020239 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA020239
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Authors: Wang X., Malaspina D. M., Hsu H.-W., Ergun R. E., and M. Horányi.
Title: The effects of magnetic fields on photoelectron-mediated spacecraft potential fluctuations
Abstract: Previously, we have experimentally studied photoelectron-mediated spacecraft potential fluctuations associated with time-dependent external electric fields. In this paper, we investigate the effects of magnetic fields on such spacecraft potential fluctuations. A magnetic field is created above the UV-illuminated surface of a spacecraft model to alter the escape rate of photoelectrons. The packet of the observed potential oscillations becomes less positive with increasing magnetic field strength because more of the emitted photoelectrons are returned to the surface. As a result, the photoelectric charging time is increased, corresponding to a decrease in the response frequency of the photoemitting surface. The amplitude of the potential oscillations decreases when the response frequency bec. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7319 - 7326 DOI: 10.1002/jgra.v119.910.1002/2014JA019923 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA019923
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Authors: Shiokawa Kazuo, Yokoyama Yu, Ieda Akimasa, Miyoshi Yoshizumi, Nomura Reiko, et al.
Title: Ground-based ELF/VLF chorus observations at subauroral latitudes-VLF-CHAIN Campaign
Abstract: We report observations of very low frequency (VLF) and extremely low frequency (ELF) chorus waves taken during the ELF/VLF Campaign observation with High-resolution Aurora Imaging Network (VLF-CHAIN) of 17–25 February 2012 at subauroral latitudes at Athabasca (L=4.3), Canada. ELF/VLF waves were measured continuously with a sampling rate of 100 kHz to monitor daily variations in ELF/VLF emissions and derive their detailed structures. We found quasiperiodic (QP) emissions whose repetition period changes rapidly within a period of 1 h without corresponding magnetic pulsations. QP emissions showed positive correlation between amplitude and frequency sweep rate, similarly to rising-tone elements. We found an event of nearly simultaneous enhancements of QP emissions and Pc1/electromagnetic ion. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7363 - 7379 DOI: 10.1002/jgra.v119.910.1002/2014JA020161 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA020161
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Authors: Fuselier S. A., Lewis W. S., Schiff C., Ergun R., Burch J L, et al.
Title: Magnetospheric Multiscale Science Mission Profile and Operations
Abstract: The Magnetospheric Multiscale (MMS) mission and operations are designed to provide the maximum reconnection science. The mission phases are chosen to investigate reconnection at the dayside magnetopause and in the magnetotail. At the dayside, the MMS orbits are chosen to maximize encounters with the magnetopause in regions where the probability of encountering the reconnection diffusion region is high. In the magnetotail, the orbits are chosen to maximize encounters with the neutral sheet, where reconnection is known to occur episodically. Although this targeting is limited by engineering constraints such as total available fuel, high science return orbits exist for launch dates over most of the year. The tetrahedral spacecraft formation has variable spacing to determine the optimum se. . .
Date: 09/2014 Publisher: Space Science Reviews DOI: 10.1007/s11214-014-0087-x Available at: http://link.springer.com/content/pdf/10.1007/s11214-014-0087-x
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Authors: Gamayunov K. V., Engebretson M. J., Zhang M., and Rassoul H. K.
Title: Model of electromagnetic ion cyclotron waves in the inner magnetosphere
Abstract: The evolution of He+-mode electromagnetic ion cyclotron (EMIC) waves is studied inside the geostationary orbit using our global model of ring current (RC) ions, electric field, plasmasphere, and EMIC waves. In contrast to the approach previously used by Gamayunov et al. (2009), however, we do not use the bounce-averaged wave kinetic equation but instead use a complete, nonbounce-averaged, equation to model the evolution of EMIC wave power spectral density, including off-equatorial wave dynamics. The major results of our study can be summarized as follows. (1) The thermal background level for EMIC waves is too low to allow waves to grow up to the observable level during one pass between the “bi-ion latitudes” (the latitudes where the given wave frequency is equal to the O+–He+ bi-io. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7541 - 7565 DOI: 10.1002/jgra.v119.910.1002/2014JA020032 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA020032
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Authors: Bergeot Nicolas, Chevalier Jean-Marie, Bruyninx Carine, Pottiaux Eric, Aerts Wim, et al.
Title: Near real-time ionospheric monitoring over Europe at the Royal Observatory of Belgium using GNSS data
Abstract: Various scientific applications and services increasingly demand real-time information on the effects of space weather on Earth’s atmosphere. In this frame, the Royal Observatory of Belgium (ROB) takes advantage of the dense EUREF Permanent GNSS Network (EPN) to monitor the ionosphere over Europe from the measured delays in the GNSS signals, and provides publicly several derived products. The main ROB products consist of ionospheric vertical Total Electron Content (TEC) maps over Europe and their variability estimated in near real-time every 15 min on 0.5° × 0.5° grids using GPS observations. The maps are available online with a latency of ~3 min in IONEX format at ftp://gnss.oma.be and as interactive web pages at www.gnss.be. This paper presents the method used in the ROB-IONO softwa. . .
Date: 09/2014 Publisher: Journal of Space Weather and Space Climate Pages: A31 DOI: 10.1051/swsc/2014028 Available at: http://www.swsc-journal.org/10.1051/swsc/2014028
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Authors: Baker Daniel
Title: New Twists in Earth’s Radiation Belts
Abstract: In 1958, an early satellite, Explorer I, made the discovery that Earth is enshrouded in belts of extraordinarily high-energy, high-intensity radiation. Now called the Van Allen belts, after the researcher who led that satellite mission, these rings are known to wax and wane in intensity, for reasons that are still being investigated. Satellites now criss-cross these belts, so understanding what influences them has dire implications for communications and other technologies in our modern age. Solar storms and space weather can pump them up, making the radiation zones around Earth immensely more dangerous for days or even weeks on end. The author has been involved with instruments on the dual Radiation Belt Storm Probes satellites that were launched on August 30, 2012, into Earth orbit to st. . .
Date: 09/2014 Publisher: American Scientist Pages: 374 DOI: 10.1511/2014.110.374 Available at: http://www.americanscientist.org/issues/feature/2014/5/new-twists-in-earths-radiation-belts
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Authors: Simms Laura E., Pilipenko Viacheslav, Engebretson Mark J, Reeves Geoffrey D, Smith A. J., et al.
Title: Prediction of relativistic electron flux at geostationary orbit following storms: Multiple regression analysis
Abstract: Many solar wind and magnetosphere parameters correlate with relativistic electron flux following storms. These include relativistic electron flux before the storm; seed electron flux; solar wind velocity and number density (and their variation); interplanetary magnetic field Bz, AE and Kp indices; and ultra low frequency (ULF) and very low frequency (VLF) wave power. However, as all these variables are intercorrelated, we use multiple regression analyses to determine which are the most predictive of flux when other variables are controlled. Using 219 storms (1992–2002), we obtained hourly averaged electron fluxes for outer radiation belt relativistic electrons (>1.5 MeV) and seed electrons (100 keV) from Los Alamos National Laboratory spacecraft (geosynchronous orbit). For each storm. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7297 - 7318 DOI: 10.1002/jgra.v119.910.1002/2014JA019955 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA019955
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Authors: Gkioulidou Matina, Ukhorskiy A., Mitchell D G, Sotirelis T., Mauk B., et al.
Title: The role of small-scale ion injections in the buildup of Earth's ring current pressure: Van Allen Probes observations of the March 17 th , 2013 storm
Abstract: Energetic particle transport into the inner magnetosphere during geomagnetic storms is responsible for significant plasma pressure enhancement, which is the driver of large-scale currents that control the global electrodynamics within the magnetosphere-ionosphere system. Therefore, understanding the transport of plasma from the tail deep into the near-Earth magnetosphere, as well as the energization processes associated with this transport, is essential for a comprehensive knowledge of the near-Earth space environment. During the main phase of a geomagnetic storm on March 17th 2013 (minimum Dst ~ −137 nT), the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on the Van Allen Probes observed frequent, small-scale proton injections deep into the inner nightsi. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020096 Available at: http://doi.wiley.com/10.1002/2014JA020096
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Authors: Glauert Sarah A, Horne Richard B, and Meredith Nigel P
Title: Simulating the Earth's radiation belts: Internal acceleration and continuous losses to the magnetopause
Abstract: In the Earth's radiation belts the flux of relativistic electrons is highly variable, sometimes changing by orders of magnitude within a few hours. Since energetic electrons can damage satellites it is important to understand the processes driving these changes and, ultimately, to develop forecasts of the energetic electron population. One approach is to use three-dimensional diffusion models, based on a Fokker-Planck equation. Here we describe a model where the phase-space density is set to zero at the outer L∗ boundary, simulating losses to the magnetopause, using recently published chorus diffusion coefficients for 1.5≤L∗≤10. The value of the phase-space density on the minimum-energy boundary is determined from a recently published, solar wind-dependent, statistical model. Our s. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7444 - 7463 DOI: 10.1002/jgra.v119.910.1002/2014JA020092 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA020092
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Authors: Goldstein J, De Pascuale S., Kletzing C., Kurth W., Genestreti K. J., et al.
Title: Simulation of Van Allen Probes Plasmapause Encounters
Abstract: We use an E × B-driven plasmapause test particle (PTP) simulation to provide global contextual information for in situ measurements by the Van Allen Probes (RBSP) during 15–20 January 2013. During 120 h of simulation time beginning on 15 January, geomagnetic activity produced three plumes. The third and largest simulated plume formed during enhanced convection on 17 January, and survived as a rotating, wrapped, residual plume for tens of hours. To validate the simulation, we compare its output with RBSP data. Virtual RBSP satellites recorded 28 virtual plasmapause encounters during 15–19 January. For 26 of 28 (92%) virtual crossings, there were corresponding actual RBSP encounters with plasmapause density gradients. The mean difference in encounter time between model and data is. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020252 Available at: http://doi.wiley.com/10.1002/2014JA020252
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Authors: Zheng Liheng, Chan Anthony A, Albert Jay M, Elkington Scot R, Koller Josef, et al.
Title: Three-dimensional stochastic modeling of radiation belts in adiabatic invariant coordinates
Abstract: A 3-D model for solving the radiation belt diffusion equation in adiabatic invariant coordinates has been developed and tested. The model, named Radbelt Electron Model, obtains a probabilistic solution by solving a set of Itô stochastic differential equations that are mathematically equivalent to the diffusion equation. This method is capable of solving diffusion equations with a full 3-D diffusion tensor, including the radial-local cross diffusion components. The correct form of the boundary condition at equatorial pitch angle α0=90° is also derived. The model is applied to a simulation of the October 2002 storm event. At α0 near 90°, our results are quantitatively consistent with GPS observations of phase space density (PSD) increases, suggesting dominance of radial diffusion; at sm. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7615 - 7635 DOI: 10.1002/jgra.v119.910.1002/2014JA020127 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA020127
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Authors: Ma Q, Li W, Chen L, Thorne R M, Kletzing C A, et al.
Title: The trapping of equatorial magnetosonic waves in the Earth's outer plasmasphere
Abstract: We investigate the excitation and propagation of equatorial magnetosonic waves observed by the Van Allen Probes and describe evidence for a trapping mechanism for magnetosonic waves in the Earth's plasmasphere. Intense equatorial magnetosonic waves were observed inside the plasmasphere in association with a pronounced proton ring distribution, which provides free energy for wave excitation. Instability analysis along the inbound orbit demonstrates that broadband magnetosonic waves can be excited over a localized spatial region near the plasmapause. The waves can subsequently propagate into the inner plasmasphere and remain trapped over a limited radial extent, consistent with the predictions of near-perpendicular propagation. By performing a similar analysis on another observed magnetosoni. . .
Date: 09/2014 Publisher: Geophysical Research Letters Pages: 6307 - 6313 DOI: 10.1002/2014GL061414 Available at: http://doi.wiley.com/10.1002/2014GL061414
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Authors: Reeves G D, Spence H E, Henderson M G, Tu W., Cunningham G. S., et al.
Title: Acceleration and loss driven by VLF chorus: Van Allen Probes observations and DREAM model results
Abstract: For over a decade now we have understood the response of the Earth's radiation belts to solar wind driving are a delicate balance of acceleration and loss processes. Theory has shown that the interaction of relativistic electrons with VLF whistler mode chorus can produce both energization through momentum diffusion and loss through pitch angle diffusion. Recent results from the Van Allen Probes mission has confirmed observationally that chorus can produce both acceleration and loss. The Van Allen Probes satellites are able to measure all the critical particle populations and wave fields with unprecedented precision and resolution but only at the two spacecraft locations. Those spatially-localized observations can be extended globally using three-dimensional diffusion codes such as the DREA. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929879 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929879
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Authors: Li W, Ni B, Thorne R M, Bortnik J, Green J C, et al.
Title: Calculation of whistler-mode wave intensity using energetic electron precipitation
Abstract: The energetic electron population measured by multiple low-altitude POES satellites is used to infer whistlermode wave amplitudes using a physics-based inversion technique. We validate this technique by quantitatively analyzing a conjunction event between the Van Allen Probes and POES, and find that the inferred hiss wave amplitudes from POES electron measurements agree remarkably well with directly measured hiss waves amplitudes. We also use this technique to construct the global distribution of chorus wave intensity with extensive coverage over a broad L-MLT region during the 8–9 October 2012 storm and demonstrate that the inferred chorus wave amplitudes agree well with conjugate measurements of chorus wave amplitudes from the Van Allen Probes. The evolution of the whistler-mode wave i. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929965 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929965
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Authors: Su Zhenpeng, Xiao Fuliang, Zheng Huinan, and Zhu Hui
Title: Chorus-driven acceleration of radiation belt electrons in the unusual temporal/spatial regions
Abstract: Cyclotron resonance with whistler-mode chorus waves is an important mechanism for the local acceleration of radiation belt energetic electrons. Such acceleration process has been widely investigated during the storm times, and its favored region is usually considered to be the low-density plasmatrough with magnetic local time (MLT) from midnight through dawn to noon. Here we present two case studies on the chorus-driven acceleration of radiation belt electrons in some “unusual” temporal /spatial regions. (1) The first event recorded by the Van Allen Probes during the nonstorm times from 21 to 23 February 2013. Within two days, a new radiation belt centering around L=5.8 formed and gradually merged with the original outer belt. The corresponding relativistic electron fluxes increased by. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929875 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929875
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Authors: Lui A. T. Y., Mitchell D G, and Lanzerotti L J
Title: Comparison of Energetic Electron Intensities Outside and Inside the Radiation Belts
Abstract: The intensities of energetic electrons (~25 – 800 keV) outside and inside Earth's radiation belts are reported using measurements from THEMIS and Van Allen Probes during non-geomagnetic storm periods. Three intervals of current disruption/dipolarization events in August, 2013 were selected for comparison. The following results are obtained. (1) Phase space densities (PSDs) for the equatorially mirroring electron population at three values of the first adiabatic invariant (20, 70, and 200 MeV/G) at the outer radiation belt boundary are found to be one to three orders of magnitude higher than values measured just inside the radiation belt. (2) There is indication that substorm activity leads to PSD increases inside L = 5.5 in less than 1 hr. (3) Evidence for progressive inward tr. . .
Date: 08/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020049 Available at: http://doi.wiley.com/10.1002/2014JA020049
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Authors: Whittaker Ian C., Rodger Craig J., Clilverd Mark A., and Sauvaud é
Title: The effects and correction of the geometric factor for the POES/MEPED electron flux instrument using a multisatellite comparison
Abstract: Measurements from the Polar-Orbiting Environmental Satellite (POES) Medium Energy Proton and Electron Detector (MEPED) instrument are widely used in studies into radiation belt dynamics and atmospheric coupling. However, this instrument has been shown to have a complex energy-dependent response to incident particle fluxes, with the additional possibility of low-energy protons contaminating the electron fluxes. We test the recent Monte Carlo theoretical simulation of the instrument by comparing the responses against observations from an independent experimental data set. Our study examines the reported geometric factors for the MEPED electron flux instrument against the high-energy resolution Instrument for Detecting Particles (IDPs) on the Detection of Electromagnetic Emissions Transmitted. . .
Date: 08/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 6386 - 6404 DOI: 10.1002/2014JA020021 Available at: http://doi.wiley.com/10.1002/2014JA020021
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Authors: Li W, Mourenas D., Artemyev A., Agapitov O., Bortnik J, et al.
Title: Evidence of stronger pitch angle scattering loss caused by oblique whistler-mode waves as compared with quasi-parallel waves
Abstract: Wave normal distributions of lower-band whistler-mode waves observed outside the plasmapause exhibit two peaks; one near the parallel direction and the other at very oblique angles. We analyze a number of conjunction events between the Van Allen Probes near the equatorial plane and POES satellites at conjugate low altitudes, where lower-band whistler-mode wave amplitudes were inferred from the two-directional POES electron measurements over 30–100 keV, assuming that these waves were quasi-parallel. For conjunction events, the wave amplitudes inferred from the POES electron measurements were found to be overestimated as compared with the Van Allen Probes measurements primarily for oblique waves and quasi-parallel waves with small wave amplitudes (< ~20 pT) measured at low latitudes. This . . .
Date: 08/2014 Publisher: Geophysical Research Letters Pages: n/a - n/a DOI: 10.1002/2014GL061260 Available at: http://doi.wiley.com/10.1002/2014GL061260
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Authors: Thomas Evan G., Yan Jingye, Zhang Jiaojiao, Baker Joseph B. H., Ruohoniemi Michael, et al.
Title: An examination of the source of decameter-scale irregularities in the geomagnetically disturbed mid-latitude ionosphere
Abstract: We present first results from a study of the plasma instability mechanism responsible for the small-scale (∼10 m) ionospheric density irregularities commonly observed by the Super Dual Auroral Radar Network (SuperDARN) HF radars in the vicinity of Sub Auroral Polarization Streams (SAPS) during periods of geomagnetic disturbance. A focus is placed on the mid-latitude region of the ionosphere over North America where recent expansion of the SuperDARN network allows for extensive direct comparisons with total electron content (TEC) measurements from a dense network of ground-based GPS receivers. The TEC observations indicate that high-speed SAPS channels and the associated small-scale irregularities are typically located within the mid-latitude ionospheric trough. The Millstone Hill Incoher. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929853 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929853
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Authors: 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: http://doi.wiley.com/10.1002/grl.v41.16http://doi.wiley.com/10.1002/2014GL061380
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Authors: Chen Lunjin, Thorne Richard M, Bortnik Jacob, Li Wen, Horne Richard B, et al.
Title: Generation of Unusually Low Frequency Plasmaspheric Hiss
Abstract: It has been reported from Van Allen Probe observations that plasmaspheric hiss intensification in the outer plasmasphere, associated with a substorm injection on Sept 30 2012, occurred with a peak frequency near 100 Hz, well below the typical plasmaspheric hiss frequency range, extending down to ~20 Hz. We examine this event of unusually low frequency plasmaspheric hiss to understand its generation mechanism. Quantitative analysis is performed by simulating wave ray paths via the HOTRAY ray tracing code with measured plasma density and calculating ray path-integrated wave gain evaluated using the measured energetic electron distribution. We demonstrate that the growth rate due to substorm injected electrons is positive but rather weak, leading to small wave gain (~10 dB) during a sin. . .
Date: 08/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL060628 Available at: http://doi.wiley.com/10.1002/2014GL060628
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Authors: Foster J C
Title: Imaging the plasmasphere with ground based GPS TEC observations and comparisons with in situ plasmaspheric observations with Van Allen Probes
Abstract: For over a decade, incoherent scatter radar observations of the mid and auroral-latitude ionosphere combined with ground based GPS observations of total electron content (TEC) have been used to study the intense storm enhanced density (SED) plumes that form over the Americas during major geomagnetic storms [1]. Magnetic field mapping of the ionospheric observations to magnetospheric heights revealed close correspondence between the SED and plasmasphere erosion plumes observed from space in EUV imagery by the IMAGE satellite [2]. During the current solar cycle the global distribution of GPS receivers used in creating the TEC maps and movies has increased significantly providing near-continuous two-dimensional coverage of TEC morphology and dynamics over much the northern hemisphere mid and . . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929943 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929943
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Authors: Foster John C, and Erickson Philip J.
Title: Initial observations of plasma waves in the sub-auroral polarization stream with the Van Allen Probes
Abstract: The Sub-Auroral Polarization Stream (SAPS) is a geospace boundary layer phenomenon associated with the interaction of the warm plasma of the magnetospheric ring current with the cold ions and electrons of the outer plasmasphere [1]. Driven by ring current enhancements during magnetospheric disturbances, SAPS location, intensity, and characteristics are greatly influenced by the underlying ionosphere. Strong M-I coupling by means of field-aligned currents creates a high-speed (>1000 m/s) westward plasma flow channel in the ionosphere at pre-midnight/post-noon local times which is readily observable by incoherent scatter [2] and HF radars and in plasma drift observations by low-altitude spacecraft (e.g. DMSP). The fast ionospheric flows generate E-region irregularities providing for addition. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929852 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929852
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Authors: Summers Danny, and Shi Run
Title: Limiting energy spectrum of an electron radiation belt
Abstract: To determine the Kennel-Petschek limiting particle flux in a planetary radiation belt in a fully relativistic regime, without assuming a predetermined form for the particle energy distribution, has been a long-standing challenge in space physics. In this paper, for the case of whistler mode wave-electron interaction, we meet this challenge. The limiting flux is determined by a steady state marginal stability criterion in which a convective wave gain condition is applied over all frequencies for which wave growth occurs. This condition produces an integral equation for the trapped flux. We find that in the relativistic regime the limiting electron energy spectrum varies asymptotically as 1/E, for large energy E, just as in the nonrelativistic case. However, the scaling coefficient in the re. . .
Date: 08/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 6313 - 6326 DOI: 10.1002/2014JA020250 Available at: http://doi.wiley.com/10.1002/2014JA020250
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Authors: Malaspina D. M., Andersson L., Ergun R. E., Wygant J R, Bonnell J W, et al.
Title: Nonlinear Electric Field Structures in the Inner Magnetosphere
Abstract: Van Allen Probes observations are presented which demonstrate the presence of nonlinear electric field structures in the inner terrestrial magnetosphere (< 6 RE). A range of structures are observed, including phase space holes and double layers.These structures are observed over several Earth radii in radial distance and over a wide range of magnetic local times. They are observed in the dusk, midnight, and dawn sectors, with the highest concentration pre-midnight. Some nonlinear electric field structures are observed to coincide with dipolarizations of the magnetic field and increases in electron energy flux for energies between 1 keV and 30 keV. Nonlinear electric field structures possess isolated impulsive electric fields, often with a significant component parallel to the ambient m. . .
Date: 08/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL061109 Available at: http://doi.wiley.com/10.1002/2014GL061109
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Authors: Selesnick R. S., Baker D N, Jaynes A. N., Li X, Kanekal S G, et al.
Title: Observations of the inner radiation belt: CRAND and trapped solar protons
Abstract: Measurements of inner radiation belt protons have been made by the Van Allen Probes Relativistic Electron-Proton Telescopes as a function of kinetic energy (24 to 76 MeV), equatorial pitch angle, and magnetic L shell, during late-2013 and early-2014. A probabilistic data analysis method reduces background from contamination by higher energy protons. Resulting proton intensities are compared to predictions of a theoretical radiation belt model. Then trapped protons originating both from cosmic ray albedo neutron decay (CRAND) and from trapping of solar protons are evident in the measured distributions. An observed double-peaked distribution in L is attributed, based on the model comparison, to a gap in the occurrence of solar proton events during the 2007 to 2011 solar minimum. Equatorial. . .
Date: 08/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020188 Available at: http://doi.wiley.com/10.1002/2014JA020188
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Authors: Kletzing Craig A.
Title: Progress on understanding chorus emissions from data of the electric and magnetic field instrument suite and integrated science (EMFISIS) on the Van Allen Probes
Abstract: The physics of the creation, loss, and transport of radiation belt particles is intimately connected to the electric and magnetic fields which mediate these processes. A key wave-particle interaction important to both acceleration and loss in the radiation belts is the of whistler-mode chorus interacting with energetic electrons. To measure this important radiation belt interaction, the two-satellite Van Allen Probes mission utilizes one of the most complete sets of measurements ever made in the inner magnetosphere. As part of the mission, the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) investigation is an integrated set of instruments consisting of a tri-axial fluxgate magnetometer (MAG) and a Waves instrument which includes a tri-axial search coil magnet. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929872 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929872
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Authors: Foster John C, and Erickson Philip J.
Title: Prompt energization of relativistic and highly relativistic electrons during a substorm interval
Abstract: On 17 March 2013, a large magnetic storm significantly depleted the multi-MeV radiation belt. We present multi-instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ∼6 Re in the midnight sector magnetosphere and from ground-based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi-MeV electrons [1]. A 50% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. Chorus is excited following the injection of low-energy (1–30 keV) plasma sheet electrons into the inner magnetosphere [2]. During the 17 March substorm injection, cold plasma that had circulated into the nightside. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929876 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929876
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Authors: Thorne R M, Li W, Ma Q, Ni B, and Bortnik J
Title: Radiation belt electron acceleration by chorus waves during the 17 March 2013 storm
Abstract: Local acceleration driven by whistler-mode chorus waves is suggested to be fundamentally important for accelerating seed electron population to ultra-relativistic energies in the outer radiation belt. In this study, we quantitatively evaluate chorus-driven electron acceleration during the 17 March 2013 storm, when Van Allen Probes observed very rapid electron acceleration up to multi MeV within ∼15 hours. A clear peak in electron phase space density observed at L∗ ∼ 4 indicates that the internal local acceleration process was operating. We construct the global distribution of chorus wave intensity from the low-altitude electron measurements by multiple POES satellites over a broad L-MLT region, which is used to simulate the radiation belt electron dynamics driven by chorus waves. Our. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929882 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929882
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Authors: McCarthy Michael P., Millan Robyn M., Sample John G., and Smith David M.
Title: Radiation belt losses observed from multiple stratospheric balloons over Antarctica
Abstract: Relativistic electrons, trapped by Earth's magnetic field, have received increasing attention since increasing numbers of commercial and research spacecraft traverse regions of high radiation flux. The Van Allen probes were launched into Earth's radiation belts in September 2012, making comprehensive measurements of charged particle fluxes and electromagnetic fields, with the objective of a better understanding of the processes that modulate radiation belt fluxes. Because losses of radiation belt electrons to Earth's atmosphere are very difficult to measure from high altitude spacecraft, a balloon-based program, consisting of campaigns in January 2013 and 2014, was funded to measure losses in conjunction with the Van Allen probes mission. We present results from both balloon campaigns, whi. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929960 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929960
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Authors: Khazanov G., Sibeck D., Tel'nikhin A., and Kronberg T.
Title: Relativistic electron precipitation events driven by electromagnetic ion-cyclotron waves
Abstract: We adopt a canonical approach to describe the stochastic motion of relativistic belt electrons and their scattering into the loss cone by nonlinear EMIC waves. The estimated rate of scattering is sufficient to account for the rate and intensity of bursty electron precipitation. This interaction is shown to result in particle scattering into the loss cone, forming ∼10 s microbursts of precipitating electrons. These dynamics can account for the statistical correlations between processes of energization, pitch angle scattering, and relativistic electron precipitation events, that are manifested on large temporal scales of the order of the diffusion time ∼tens of minutes.
Date: 08/2014 Publisher: Physics of Plasmas Pages: 082901 DOI: 10.1063/1.4892185 Available at: http://scitation.aip.org/content/aip/journal/pop/21/8/10.1063/1.4892185
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Authors: Boynton R. J., Balikhin M. A., and Mourenas D.
Title: Statistical analysis of electron lifetimes at GEO: Comparisons with chorus-driven losses
Abstract: The population of electrons in the Earth's outer radiation belt increases when the magnetosphere is exposed to high-speed streams of solar wind, coronal mass ejections, magnetic clouds, or other disturbances. After this increase, the number of electrons decays back to approximately the initial population. This study statistically analyzes the lifetimes of the electron at Geostationary Earth Orbit (GEO) from Los Alamos National Laboratory electron flux data. The decay rate of the electron fluxes are calculated for 14 energies ranging from 24 keV to 3.5 MeV to identify a relationship between the lifetime and energy of the electrons. The statistical data show that electron lifetimes increase with energy. Also, the statistical results show a good agreement up to ∼1 MeV with an analytical mod. . .
Date: 08/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 6356 - 6366 DOI: 10.1002/2014JA019920 Available at: http://doi.wiley.com/10.1002/2014JA019920
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Authors: Santolik O, Hospodarsky G B, Kurth W S, Averkamp T. F., Kletzing C A, et al.
Title: Statistical properties of wave vector directions of whistler-mode waves in the radiation belts based on measurements of the Van Allen probes and Cluster missions
Abstract: Wave-particle interactions in the Earth's Van Allen radiation belts are known to be an efficient process of the exchange of energy between different particle populations, including the energetic radiation belt particles. The whistler mode waves, especially chorus, can control the radiation belt dynamics via linear or nonlinear interactions with both the energetic radiation belt electrons and lower energy electron populations. Wave vector directions are a very important parameter of these wave-particle interactions. We use measurements of whistlermode waves by the WAVES instrument from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard the Van Allen Probes spacecraft covering the equatorial region of the Earth's magnetosphere in all MLT sectors, and a . . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929880 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929880
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Authors: Makela Jonathan J., Harding Brian J., Meriwether John W., Mesquita Rafael, Sanders Samuel, et al.
Title: Storm time response of the mid-latitude thermosphere: Observations from a network of Fabry-Perot interferometers
Abstract: Observations of thermospheric neutral winds and temperatures obtained during a geomagnetic storm on 2 October 2013 from a network of six Fabry-Perot interferometers (FPIs) deployed in the midwest United States are presented. Coincident with the commencement of the storm, the apparent horizontal wind is observed to surge westward and southward (towards the equator). Simultaneous to this surge in the apparent horizontal winds, an apparent downward wind of approximately 100 m/s lasting for 6 hours is observed. The apparent neutral temperature is observed to increase by approximately 400 K over all of the sites. Observations from an all-sky imaging system operated at the Millstone Hill observatory indicate the presence of a stable auroral red (SAR) arc and diffuse red aurora during this . . .
Date: 08/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA019832 Available at: http://doi.wiley.com/10.1002/2014JA019832
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Authors: Artemyev A. V., Agapitov O. V., Mozer F, and Krasnoselskikh V.
Title: Thermal electron acceleration by localized bursts of electric field in the radiation belts
Abstract: In this paper we investigate the resonant interaction of thermal ~10−100 eV electrons with a burst of electrostatic field that results in electron acceleration to kilovolt energies. This single burst contains a large parallel electric field of one sign and a much smaller, longer lasting parallel field of the opposite sign. The Van Allen Probe spacecraft often observes clusters of spatially localized bursts in the Earth's outer radiation belts. These structures propagate mostly away from thegeomagnetic equator and share properties of soliton-like nonlinear electron-acoustic waves: a velocity of propagation is about the thermal velocity of cold electrons (~3000−10000 km/s), and a spatial scale of electric field localization alongthe field lines is about the Debye radius of hot electrons . . .
Date: 08/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL061248 Available at: http://doi.wiley.com/10.1002/2014GL061248
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Authors: Schultz Colin
Title: Boom and bust for radiation belt high-energy electron populations
Abstract: Launched on 30 August 2012, the twin Van Allen probes constitute the first dedicated mission in decades to study the Earth's radiation belts. The sensor-laden spacecraft follow a nearly equatorial orbit, which gives them a complete view of the full range of radiation belt processes. In a new study, Baker et al. lay out some of the surprising results unveiled by the crafts' first year in orbit.
Date: 07/2014 Publisher: Eos, Transactions American Geophysical Union Pages: 260 - 260 DOI: 10.1002/eost.v95.2810.1002/2014EO280021 Available at: http://doi.wiley.com/10.1002/2014EO280021
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Authors: Balcerak Ernie
Title: Bursty flows in magnetosphere influence ionosphere
Abstract: In Earth's plasma sheet—a region of dense ionized gas that lies around the equatorial plane and extends into the magnetotail—plasma flows in large-scale smooth flows as well as in small-scale bursts. Studies have investigated the individual bursty flows but not the large-scale effects of these bursts. To investigate how the bursty flows affect the magnetosphere and its coupling to the ionosphere, Yang et al. conducted two simulations, one with only large-scale flows and the other with random bubbles and blobs of plasma flowing both toward Earth and away from it. They found that the bursty flows significantly altered the magnetic properties of the plasma sheet and the distributions of current in the ionosphere and that the properties found in the bursty flow simulations matched observat. . .
Date: 07/2014 Publisher: Eos, Transactions American Geophysical Union Pages: 260 - 260 DOI: 10.1002/eost.v95.2810.1002/2014EO280019 Available at: http://doi.wiley.com/10.1002/eost.v95.28http://doi.wiley.com/10.1002/2014EO280019
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Authors: Mozer S., Agapitov O., Krasnoselskikh V., Lejosne S., Reeves D., et al.
Title: Direct Observation of Radiation-Belt Electron Acceleration from Electron-Volt Energies to Megavolts by Nonlinear Whistlers
Abstract: The mechanisms for accelerating electrons from thermal to relativistic energies in the terrestrial magnetosphere, on the sun, and in many astrophysical environments have never been verified. We present the first direct observation of two processes that, in a chain, cause this acceleration in Earth’s outer radiation belt. The two processes are parallel acceleration from electron-volt to kilovolt energies by parallel electric fields in time-domain structures (TDS), after which the parallel electron velocity becomes sufficiently large for Doppler-shifted upper band whistler frequencies to be in resonance with the electron gyration frequency, even though the electron energies are kilovolts and not hundreds of kilovolts. The electrons are then accelerated by the whistler perpendicular electri. . .
Date: 07/2014 Publisher: Physical Review Letters DOI: 10.1103/PhysRevLett.113.035001 Available at: http://link.aps.org/doi/10.1103/PhysRevLett.113.035001
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Authors: Mozer F S, Agapitov O., Krasnoselskikh V., Lejosne S., Reeves G D, et al.
Title: Direct Observation of Radiation-Belt Electron Acceleration from Electron-Volt Energies to Megavolts by Nonlinear Whistlers
Abstract: The mechanisms for accelerating electrons from thermal to relativistic energies in the terrestrial magnetosphere, on the sun, and in many astrophysical environments have never been verified. We present the first direct observation of two processes that, in a chain, cause this acceleration in Earth’s outer radiation belt. The two processes are parallel acceleration from electron-volt to kilovolt energies by parallel electric fields in time-domain structures (TDS), after which the parallel electron velocity becomes sufficiently large for Doppler-shifted upper band whistler frequencies to be in resonance with the electron gyration frequency, even though the electron energies are kilovolts and not hundreds of kilovolts. The electrons are then accelerated by the whistler perpendicular electri. . .
Date: 07/2014 Publisher: Phys. Rev. Lett. Pages: 035001 DOI: 10.1103/PhysRevLett.113.035001 Available at: http://link.aps.org/doi/10.1103/PhysRevLett.113.035001
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Authors: Sarris T. E.
Title: Estimates of the power per mode number of broadband ULF waves at geosynchronous orbit
Abstract: In studies of radial diffusion processes in the magnetosphere it is well known that ultralow frequency (ULF) waves of frequency mωd can resonantly interact with particles of drift frequency ωd, where m is the waves' azimuthal mode number. Due to difficulties in estimating m, an oversimplifying assumption is often made in simulations, namely that all ULF wave power is located at a single mode number. In this paper a technique is presented for extracting information on the distribution of ULF power in a range of azimuthal mode numbers. As a first step, the cross power and phase differences between time series from azimuthally aligned magnetometers are calculated. Subsequently, through integrating the ULF power at particular ranges of phase differences that correspond to particular mode num. . .
Date: 07/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 5539 - 5550 DOI: 10.1002/2013JA019238 Available at: http://doi.wiley.com/10.1002/2013JA019238
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Authors: Nishimura Y., Bortnik J, Li W, Lyons L R, Donovan E. F., et al.
Title: Evolution of nightside subauroral proton aurora caused by transient plasma sheet flows
Abstract: While nightside subauroral proton aurora shows rapid temporal variations, the cause of this variability has rarely been investigated. Using well-coordinated observations by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imagers, THEMIS satellites in the equatorial magnetosphere, and the low-altitude NOAA 17 satellite, we examined the rapid temporal evolution of subauroral proton aurora in the premidnight sector. An isolated proton aurora occurred soon after an auroral poleward boundary intensification that was followed by an auroral streamer reaching the equatorward boundary of the auroral oval. Three THEMIS satellites in the magnetotail detected flow bursts and one of the THEMIS satellites in the outer plasmasphere observed a ring current injectio. . .
Date: 07/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 5295 - 5304 DOI: 10.1002/2014JA020029 Available at: http://doi.wiley.com/10.1002/2014JA020029
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Authors: Kim Kyung-Chan, and Lee Dae-Young
Title: Magnetopause structure favorable for radiation belt electron loss
Abstract: Magnetopause shadowing is regarded as one of the major reasons for the loss of relativistic radiation belt electrons, although this has not yet been fully validated by observations. Previous simulations on this process assumed that all of the electrons encountering the magnetopause are simply lost into the magnetosheath just as ring current ions can be and did not examine details of the particle dynamics across and inside the magnetopause which has a finite thickness. In this paper, we perform test particle orbit calculations based on a simplified one-dimensional magnetopause model to demonstrate specifically how relativistic electrons arriving at the prenoon side of the magnetopause can be lost. The calculation results indicate that the loss process is determined by two factors: (i) a gra. . .
Date: 07/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 5495 - 5508 DOI: 10.1002/2014JA019880 Available at: http://doi.wiley.com/10.1002/2014JA019880
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Authors: Ni Binbin, Li Wen, Thorne Richard M, Bortnik Jacob, Green Janet C, et al.
Title: A novel technique to construct the global distribution of whistler mode chorus wave intensity using low-altitude POES electron data
Abstract: Although magnetospheric chorus plays a significant role in the acceleration and loss of radiation belt electrons, its global evolution during any specific time period cannot be directly obtained by spacecraft measurements. Using the low-altitude NOAA Polar-orbiting Operational Environmental Satellite (POES) electron data, we develop a novel physics-based methodology to infer the chorus wave intensity and construct its global distribution with a time resolution of less than an hour. We describe in detail how to apply the technique to satellite data by performing two representative analyses, i.e., (i) for one specific time point to visualize the estimation procedure and (ii) for a particular time period to validate the method and construct an illustrative global chorus wave model. We demonst. . .
Date: 07/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 5685 - 5699 DOI: 10.1002/jgra.v119.710.1002/2014JA019935 Available at: http://doi.wiley.com/10.1002/jgra.v119.7http://doi.wiley.com/10.1002/2014JA019935
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