Found 21 entries in the Bibliography.
Showing entries from 1 through 21
| 2019 |
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Multiyear Measurements of Radiation Belt Electrons: Acceleration, Transport, and Loss In addition to clarifying morphological structures of the Earth\textquoterights radiation belts, it has also been a major achievement of the Van Allen Probes mission to understand more thoroughly how highly relativistic and ultrarelativistic electrons are accelerated deep inside the radiation belts. Prior studies have demonstrated that electrons up to energies of 10 megaelectron volts (MeV) can be produced over broad regions of the outer Van Allen zone on timescales of minutes to a few hours. It often is seen that geomagneti ... Baker, Daniel; Hoxie, Vaughn; Zhao, Hong; Jaynes, Allison; Kanekal, Shri; Li, Xinlin; Elkington, Scot; YEAR: 2019 DOI: 10.1029/2018JA026259 convection electric field; Energetic particle deep penetration; Low L Region; Radiation belts; Van Allen Probes |
| 2018 |
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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-relativisti ... Jaynes, A.; Ali, A.; Elkington, S.; Malaspina, D.; Baker, D.; Li, X.; Kanekal, S.; Henderson, M.; Kletzing, C.; Wygant, J.; YEAR: 2018 DOI: 10.1029/2018GL079786 Magnetosphere; radial diffusion; Radiation belts; ULF waves; Van Allen Probes |
| 2016 |
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Electric and Magnetic Radial Diffusion Coefficients Using the Van Allen Probes Data ULF waves are a common occurrence in the inner magnetosphere and they contribute to particle motion, significantly, at times. We used the magnetic and the electric field data from the EMFISIS and the EFW instruments on board the Van Allen Probes to estimate the ULF wave power in the compressional component of the magnetic field and the azimuthal component of the electric field, respectively. Using L*, Kp, and MLT as parameters, we conclude that the noon sector contains higher ULF Pc-5 wave power compared with the other MLT s ... Ali, Ashar; Malaspina, David; Elkington, Scot; Jaynes, Allison; Chan, Anthony; Wygant, John; Kletzing, Craig; YEAR: 2016 DOI: 10.1002/2016JA023002 Electric and Magnetic Components; radial diffusion; RBSP; Van Allen Probes |
| 2015 |
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On 2 October 2013, the arrival of an interplanetary shock compressed the Earth\textquoterights 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 Alfv\ en waves. ... Malaspina, David; Claudepierre, Seth; Takahashi, Kazue; Jaynes, Allison; Elkington, Scot; Ergun, Robert; Wygant, John; Reeves, Geoff; Kletzing, Craig; YEAR: 2015 DOI: 10.1002/2015GL065935 inner magnetosphere; interplanetary shock; Kinetic Alfven Waves; magnetosphere shock response; plasma waves; ULF waves; Van Allen Probes |
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During early November 2013, the magnetosphere experienced concurrent driving by a coronal mass ejection (CME) during an ongoing high-speed stream (HSS) event. The relativistic electron response to these two kinds of drivers, i.e., HSS and CME, is typically different, with the former often leading to a slower buildup of electrons at larger radial distances, while the latter energizing electrons rapidly with flux enhancements occurring closer to the Earth.We present a detailed analysis of the relativistic electron response inc ... Kanekal, S.; Baker, D.; Henderson, M.; Li, W.; Fennell, J.; Zheng, Y.; Richardson, I.; Jones, A.; Ali, A.; Elkington, S.; Jaynes, A.; Li, X.; Blake, J.; Reeves, G.; Spence, H.; Kletzing, C.; YEAR: 2015 DOI: 10.1002/2015JA021395 CME; HSS; Van Allen Probes; IP shock; relativistic electrons |
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Source and Seed Populations for Relativistic Electrons: Their Roles in Radiation Belt Changes Strong enhancements of outer Van Allen belt electrons have been shown to have a clear dependence on solar wind speed and on the duration of southward interplanetary magnetic field. However, individual case study analyses also have demonstrated that many geomagnetic storms produce little in the way of outer belt enhancements and, in fact, may produce substantial losses of relativistic electrons. In this study, focused upon a key period in August-September 2014, we use GOES geostationary orbit electron flux data and Van Allen ... Jaynes, A.N.; Baker, D.N.; Singer, H.J.; Rodriguez, J.V.; Loto\textquoterightaniu, T.M.; Ali, A.; Elkington, S.R.; Li, X.; Kanekal, S.G.; Fennell, J.F.; Li, W.; Thorne, R.M.; Kletzing, C.A.; Spence, H.E.; Reeves, G.D.; YEAR: 2015 DOI: 10.1002/2015JA021234 Radiation belts; relativistic electrons; substorms; ULF waves; Van Allen Probes; VLF waves |
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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 disti ... Ali, Ashar; Elkington, Scot; Tu, Weichao; Ozeke, Louis; Chan, Anthony; Friedel, Reiner; YEAR: 2015 DOI: 10.1002/2014JA020419 |
| 2014 |
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Three-dimensional stochastic modeling of radiation belts in adiabatic invariant coordinates 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 It\^o 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 ... Zheng, Liheng; Chan, Anthony; Albert, Jay; Elkington, Scot; Koller, Josef; Horne, Richard; Glauert, Sarah; Meredith, Nigel; YEAR: 2014 DOI: 10.1002/jgra.v119.910.1002/2014JA020127 adiabatic invariant coordinates; diffusion equation; fully 3-D model; Radiation belt; stochastic differential equation |
| 2013 |
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Particle acceleration and loss in the million electron Volt (MeV) energy range (and above) is the least understood aspect of radiation belt science. In order to measure cleanly and separately both the energetic electron and energetic proton components, there is a need for a carefully designed detector system. The Relativistic Electron-Proton Telescope (REPT) on board the Radiation Belt Storm Probe (RBSP) pair of spacecraft consists of a stack of high-performance silicon solid-state detectors in a telescope configuration, a c ... Baker, D.; Kanekal, S.; Hoxie, V.; Batiste, S.; Bolton, M.; Li, X.; Elkington, S.; Monk, S.; Reukauf, R.; Steg, S.; Westfall, J.; Belting, C.; Bolton, B.; Braun, D.; Cervelli, B.; Hubbell, K.; Kien, M.; Knappmiller, S.; Wade, S.; Lamprecht, B.; Stevens, K.; Wallace, J.; Yehle, A.; Spence, H.; Friedel, R.; YEAR: 2013 DOI: 10.1007/s11214-012-9950-9 |
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The Radiation Belt Storm Probes (RBSP)-Energetic Particle, Composition, and Thermal Plasma (ECT) suite contains an innovative complement of particle instruments to ensure the highest quality measurements ever made in the inner magnetosphere and radiation belts. The coordinated RBSP-ECT particle measurements, analyzed in combination with fields and waves observations and state-of-the-art theory and modeling, are necessary for understanding the acceleration, global distribution, and variability of radiation belt electrons and ... Spence, H.; Reeves, G.; Baker, D.; Blake, J.; Bolton, M.; Bourdarie, S.; Chan, A.; Claudpierre, S.; Clemmons, J.; Cravens, J.; Elkington, S.; Fennell, J.; Friedel, R.; Funsten, H.; Goldstein, J.; Green, J.; Guthrie, A.; Henderson, M.; Horne, R.; Hudson, M.; Jahn, J.-M.; Jordanova, V.; Kanekal, S.; Klatt, B.; Larsen, B.; Li, X.; MacDonald, E.; Mann, I.R.; Niehof, J.; O\textquoterightBrien, T.; Onsager, T.; Salvaggio, D.; Skoug, R.; Smith, S.; Suther, L.; Thomsen, M.; Thorne, R.; YEAR: 2013 DOI: DOI: 10.1007/s11214-013-0007-5 |
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Since their discovery more than 50 years ago, Earth\textquoterights Van Allen radiation belts have been considered to consist of two distinct zones of trapped, highly energetic charged particles. The outer zone is composed predominantly of megaelectron volt (MeV) electrons that wax and wane in intensity on time scales ranging from hours to days, depending primarily on external forcing by the solar wind. The spatially separated inner zone is composed of commingled high-energy electrons and very energetic positive ions (mostly ... Baker, D.; Kanekal, S.; Hoxie, V.; Henderson, M.; Li, X.; Spence, H.; Elkington, S.; Friedel, R.; Goldstein, J.; Hudson, M.; Reeves, G.; Thorne, R.; Kletzing, C.; Claudepierre, S.; YEAR: 2013 DOI: 10.1126/science.1233518 |
| 2012 |
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Radiation belt 2D and 3D simulations for CIR-driven storms during Carrington Rotation 2068 As part of the International Heliospheric Year, the Whole Heliosphere Interval, Carrington Rotation 2068, from March 20 to April 16, 2008 was chosen as an internationally coordinated observing and modeling campaign. A pair of solar wind structures identified as Corotating Interaction Regions (CIR), characteristic of the declining phase of the solar cycle and solar minimum, was identified in solar wind plasma measurements from the ACE satellite. Such structures have previously been determined to be geoeffective in producing e ... Hudson, M.; Brito, Thiago; Elkington, Scot; Kress, Brian; Li, Zhao; Wiltberger, Mike; YEAR: 2012 DOI: 10.1016/j.jastp.2012.03.017 |
| 2008 |
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This paper focuses on the modeling of local acceleration and loss processes in the outer radiation belt. We begin by reviewing the statistical properties of waves that violate the first and second adiabatic invariants, leading to the loss and acceleration of high energy electrons in the outer radiation belt. After a brief description of the most commonly accepted methodology for computing quasi-linear diffusion coefficients, we present pitch-angle scattering simulations by (i) plasmaspheric hiss, (ii) a combination of plasma ... SHPRITS, Y; SUBBOTIN, D; MEREDITH, N; ELKINGTON, S; YEAR: 2008 DOI: 10.1016/j.jastp.2008.06.014 |
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In this paper, we focus on the modeling of radial transport in the Earth\textquoterights outer radiation belt. A historical overview of the first observations of the radiation belts is presented, followed by a brief description of radial diffusion. We describe how resonant interactions with poloidal and toroidal components of the ULF waves can change the electron\textquoterights energy and provide radial displacements. We also present radial diffusion and guiding center simulations that show the importance of radial transpor ... SHPRITS, Y; ELKINGTON, S; MEREDITH, N; SUBBOTIN, D; YEAR: 2008 DOI: 10.1016/j.jastp.2008.06.008 |
| 2006 |
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In an MHD particle simulation of the September 1998 magnetic storm the evolution of the radiation belt electron radial flux profile appears to be diffusive, and diffusion caused by ULF waves has been invoked as the probable mechanism. In order to separate adiabatic and nonadiabatic effects and to investigate the radial diffusion mechanism during this storm, in this work we solve a radial diffusion equation with ULF wave diffusion coefficients and a time-dependent outer boundary condition, and the results are compared with th ... Fei, Yue; Chan, Anthony; Elkington, Scot; Wiltberger, Michael; YEAR: 2006 DOI: 10.1029/2005JA011211 |
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A review of ULF interactions with radiation belt electrons Energetic particle fluxes in the outer zone radiation belts can vary over orders of magnitude on a variety of timescales. Power at ULF frequencies, on the order of a few millihertz, have been associated with changes in flux levels among relativis- tic electrons comprising the outer zone of the radiation belts. Power in this part of the spectrum may occur as a result of a number of processes, including internally- generated waves induced by plasma instabilities, and externally generated processes such as shear instabilities a ... YEAR: 2006 DOI: 10.1029/169GM12 |
| 2005 |
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The influence of ultralow frequency (ULF) waves in the Pc5 frequency range on radiation belt electrons in a compressed dipole magnetic field is examined. This is the first analysis in three dimensions utilizing model ULF wave electric and magnetic fields on the guiding center trajectories of relativistic electrons. A model is developed, describing magnetic and electric fields associated with poloidal mode Pc5 ULF waves. The frequency and L dependence of the ULF wave power are included in this model by incorporating published ... Perry, K.; Hudson, M.; Elkington, S.; YEAR: 2005 DOI: 10.1029/2004JA010760 |
| 2003 |
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Resonant acceleration and diffusion of outer zone electrons in an asymmetric geomagnetic field [1] The outer zone radiation belt consists of energetic electrons drifting in closed orbits encircling the Earth between \~3 and 7 RE. Electron fluxes in the outer belt show a strong correlation with solar and magnetospheric activity, generally increasing during geomagnetic storms with associated high solar wind speeds, and increasing in the presence of magnetospheric ULF waves in the Pc-5 frequency range. In this paper, we examine the influence of Pc-5 ULF waves on energetic electrons drifting in an asymmetric, compressed d ... YEAR: 2003 DOI: 10.1029/2001JA009202 |
| 2002 |
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MHD/particle simulations of radiation belt dynamics Particle fluxes in the outer radiation belts can show substantial variation in time, over scales ranging from a few minutes, such as during the sudden commencement phase of geomagnetic storms, to the years-long variations associated with the progression of the solar cycle. As the energetic particles comprising these belts can pose a hazard to human activity in space, considerable effort has gone into understanding both the source of these particles and the physics governing their dynamical behavior. Computationally tracking ... ELKINGTON, S; Hudson, M.; Wiltberger, M.J; Lyon, J.; YEAR: 2002 DOI: 10.1016/S1364-6826(02)00018-4 Shock-Induced Transport. Slot Refilling and Formation of New Belts. |
| 1999 |
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There has been increasing evidence that Pc-5 ULF oscillations play a fundamental role in the dynamics of outer zone electrons. In this work we examine the adiabatic response of electrons to toroidal-mode Pc-5 field line resonances using a simplified magnetic field model. We find that electrons can be adiabatically accelerated through a drift-resonant interaction with the waves, and present expressions describing the resonance condition and half-width for resonant interaction. The presence of magnetospheric convection electri ... Elkington, Scot; Hudson, M.; Chan, Anthony; YEAR: 1999 DOI: 10.1029/1999GL003659 |
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Simulation of Radiation Belt Dynamics Driven by Solar Wind Variations The rapid rise of relativistic electron fluxes inside geosynchronous orbit during the January 10-11, 1997, CME-driven magnetic cloud event has been simulated using a relativistic guiding center test particle code driven by out-put from a 3D global MHD simulation of the event. A comparison can be made of this event class, characterized by a moderate solar wind speed (< 600 km/s), and those commonly observed at the last solar maximum with a higher solar wind speed and shock accelerated solar energetic proton component. Relati ... Hudson, M.; Elkington, S.; Lyon, J.; Goodrich, C.; Rosenberg, T.; YEAR: 1999 DOI: 10.1029/GM10910.1029/GM109p0171 |
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