Found 1095 entries in the Bibliography.

Showing entries from 851 through 900


Prediction of relativistic electron flux at geostationary orbit following storms: Multiple regression analysis

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 ...

Simms, Laura; Pilipenko, Viacheslav; Engebretson, Mark; Reeves, Geoffrey; Smith, A.; Clilverd, Mark;

YEAR: 2014     DOI: 10.1002/jgra.v119.910.1002/2014JA019955

empirical modeling; multiple regression; multivariable analysis

The role of small-scale ion injections in the buildup of Earth\textquoterights ring current pressure: Van Allen Probes observations of the March 17 th , 2013 storm

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. Durin ...

Gkioulidou, Matina; Ukhorskiy, A.; Mitchell, D.; Sotirelis, T.; Mauk, B.; Lanzerotti, L.;

YEAR: 2014     DOI: 10.1002/2014JA020096

Geomagnetic storms; Ion injections; ring current; Van Allen Probes

Simulating the Earth\textquoterights radiation belts: Internal acceleration and continuous losses to the magnetopause

In the Earth\textquoterights 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 ...

Glauert, Sarah; Horne, Richard; Meredith, Nigel;

YEAR: 2014     DOI: 10.1002/jgra.v119.910.1002/2014JA020092

magnetopause; Radiation belt; wave-particle interactions

Simulation of Van Allen Probes Plasmapause Encounters

We use an E \texttimes B-driven plasmapause test particle (PTP) simulation to provide global contextual information for in situ measurements by the Van Allen Probes (RBSP) during 15\textendash20 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 da ...

Goldstein, J.; De Pascuale, S.; Kletzing, C.; Kurth, W.; Genestreti, K.; Skoug, R.; Larsen, B.; Kistler, L.; Mouikis, C.; Spence, H.;

YEAR: 2014     DOI: 10.1002/2014JA020252

observations; plasmasphere; residual plume; simulation; Van Allen Probes

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

The trapping of equatorial magnetosonic waves in the Earth\textquoterights outer plasmasphere

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\textquoterights 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 localize ...

Ma, Q.; Li, W.; Chen, L.; Thorne, R.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Reeves, G.; Henderson, M.; Spence, H.;

YEAR: 2014     DOI: 10.1002/2014GL061414

magnetosonic waves; Van Allen Probes; wave excitation; wave propagation

Acceleration and loss driven by VLF chorus: Van Allen Probes observations and DREAM model results

For over a decade now we have understood the response of the Earth\textquoterights 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 satelli ...

Reeves, G.; Spence, H.; Henderson, M.; Tu, W.; Cunningham, G.; Chen, Y.; Blake, J.; Fennell, J.; Baker, D.;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929879

Van Allen Probes

Calculation of whistler-mode wave intensity using energetic electron precipitation

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 e ...

Li, W.; Ni, B.; Thorne, R.; Bortnik, J.; Green, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929965

Electron traps; Energy measurement; Plasma measurements; Van Allen Probes

Chorus-driven acceleration of radiation belt electrons in the unusual temporal/spatial regions

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 \textquotedblleftunusual\textquotedblright temporal /spat ...

Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan; Zhu, Hui;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929875

Acceleration; Van Allen Belts; Van Allen Probes

Comparison of Energetic Electron Intensities Outside and Inside the Radiation Belts

The intensities of energetic electrons (~25 \textendash 800 keV) outside and inside Earth\textquoterights 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 ...

T. Y. Lui, A.; Mitchell, D.; Lanzerotti, L.;

YEAR: 2014     DOI: 10.1002/2014JA020049

Dipolarization; energetic electrons; Radiation belts; substorm; Van Allen Probes

The effects and correction of the geometric factor for the POES/MEPED electron flux instrument using a multisatellite comparison

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 observati ...

Whittaker, Ian; Rodger, Craig; Clilverd, Mark; Sauvaud, \;

YEAR: 2014     DOI: 10.1002/2014JA020021

DEMETER; energetic electron flux; geometric factor; POES; Radiation belts

Evidence of stronger pitch angle scattering loss caused by oblique whistler-mode waves as compared with quasi-parallel waves

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\textendash100 keV, assuming that these waves were quasi-parallel. For conjunction ...

Li, W.; Mourenas, D.; Artemyev, A.; Agapitov, O.; Bortnik, J.; Albert, J.; Thorne, R.; Ni, B.; Kletzing, C.; Kurth, W.; Hospodarsky, G.;

YEAR: 2014     DOI: 10.1002/2014GL061260

chorus waves; electron precipitation; oblique whistler; pitch angle scattering

An examination of the source of decameter-scale irregularities in the geomagnetically disturbed mid-latitude ionosphere

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 ...

Thomas, Evan; Yan, Jingye; Zhang, Jiaojiao; Baker, Joseph; Ruohoniemi, Michael; Hoskawa, Keisuke; Erickson, Philip; Coster, Anthea; Foster, John;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929853

Ionosphere; Plasmas; SUPERDARN; Van Allen Probes

Fast transport of resonant electrons in phase space due to nonlinear trapping by whistler waves

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\textquoterights 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 op ...

Artemyev, A.; Vasiliev, A.; Mourenas, D.; Agapitov, O.; Krasnoselskikh, V.; Boscher, D.; Rolland, G.;

YEAR: 2014     DOI: 10.1002/grl.v41.1610.1002/2014GL061380

particle trapping; Radiation belts; Wave-particle interaction

Generation of Unusually Low Frequency Plasmaspheric Hiss

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 ...

Chen, Lunjin; Thorne, Richard; Bortnik, Jacob; Li, Wen; Horne, Richard; Reeves, G.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Blake, J.; Fennell, J.;

YEAR: 2014     DOI: 10.1002/2014GL060628

Chorus; Generation; Plasmaspheric Hiss; Ray Tracing; Van Allen Probes

Imaging the plasmasphere with ground based GPS TEC observations and comparisons with in situ plasmaspheric observations with Van Allen Probes

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 ...

Foster, J;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929943

magnetic fields; Magnetic resonance imaging; Magnetosphere; Van Allen Probes

Initial observations of plasma waves in the sub-auroral polarization stream with the Van Allen Probes

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 io ...

Foster, John; Erickson, Philip;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929852

Ionosphere; Magnetosphere; Van Allen Probes

Limiting energy spectrum of an electron radiation belt

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 ...

Summers, Danny; Shi, Run;

YEAR: 2014     DOI: 10.1002/2014JA020250

limiting trapped flux; Radiation belts

Nonlinear Electric Field Structures in the Inner Magnetosphere

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 coi ...

Malaspina, D.; Andersson, L.; Ergun, R.; Wygant, J.; Bonnell, J; Kletzing, C.; Reeves, G.; Skoug, R.; Larsen, B.;

YEAR: 2014     DOI: 10.1002/2014GL061109

Van Allen Probes

Observations of the inner radiation belt: CRAND and trapped solar protons

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) ...

Selesnick, R.; Baker, D.; Jaynes, A.; Li, X.; Kanekal, S.; Hudson, M.; Kress, B.;

YEAR: 2014     DOI: 10.1002/2014JA020188

Van Allen Probes

Progress on understanding chorus emissions from data of the electric and magnetic field instrument suite and integrated science (EMFISIS) on the Van Allen Probes

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 ...

Kletzing, Craig;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929872

Instruments; Magnetic field measurement; magnetic fields; Magnetometers; Magnetosphere; Van Allen Probes

Prompt energization of relativistic and highly relativistic electrons during a substorm interval

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 f ...

Foster, John; Erickson, Philip;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929876

Magnetic flux; Magnetosphere; Van Allen Belts; Van Allen Probes

Radiation belt electron acceleration by chorus waves during the 17 March 2013 storm

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 ...

Thorne, R.; Li, W.; Ma, Q.; Ni, B.; Bortnik, J.;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929882

Atmospheric waves; Van Allen Belts; Van Allen Probes

Radiation belt losses observed from multiple stratospheric balloons over Antarctica

Relativistic electrons, trapped by Earth\textquoterights 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\textquoterights 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 ...

McCarthy, Michael; Millan, Robyn; Sample, John; Smith, David;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929960

Extraterrestrial measurements; Loss measurement; Magnetosphere; Van Allen Probes

Relativistic electron precipitation events driven by electromagnetic ion-cyclotron waves

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 ...

Khazanov, G.; Sibeck, D.; Tel\textquoterightnikhin, A.; Kronberg, T.;

YEAR: 2014     DOI: 10.1063/1.4892185

Diffusion; Electron scattering; Nonlinear waves; wave-particle interactions; Whistler waves

Statistical analysis of electron lifetimes at GEO: Comparisons with chorus-driven losses

The population of electrons in the Earth\textquoterights 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 f ...

Boynton, R.; Balikhin, M.; Mourenas, D.;

YEAR: 2014     DOI: 10.1002/2014JA019920

Chorus; electron lifetimes; electron losses; oblique waves

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

Wave-particle interactions in the Earth\textquoterights 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 interacti ...

Santolik, O.; Hospodarsky, G.; Kurth, W.; Averkamp, T.; Kletzing, C.; Cornilleau-Wehrlin, N.;

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929880

Atmospheric measurements; Magnetic field measurement; Van Allen Probes

Storm time response of the mid-latitude thermosphere: Observations from a network of Fabry-Perot interferometers

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 neut ...

Makela, Jonathan; Harding, Brian; Meriwether, John; Mesquita, Rafael; Sanders, Samuel; Ridley, Aaron; Castellez, Michael; Ciocca, Marco; Earle, Gregory; Frissell, Nathaniel; Hampton, Donald; Gerrard, Andrew; Noto, John; Martinis, Carlos;

YEAR: 2014     DOI: 10.1002/2014JA019832

geomagnetic storm response; thermospheric winds; Van Allen Probes

Thermal electron acceleration by localized bursts of electric field in the radiation belts

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\textquoterights outer radiation belts. These structures propagate mostly away from thegeomagnetic equator a ...

Artemyev, A.; Agapitov, O.; Mozer, F.; Krasnoselskikh, V.;

YEAR: 2014     DOI: 10.1002/2014GL061248

Radiation belts; thermal electrons; Van Allen Probes; Wave-particle interaction

Boom and bust for radiation belt high-energy electron populations

Launched on 30 August 2012, the twin Van Allen probes constitute the first dedicated mission in decades to study the Earth\textquoterights 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\textquoteright first year in orbit.

Schultz, Colin;

YEAR: 2014     DOI: 10.1002/eost.v95.2810.1002/2014EO280021

Van Allen Probes

Bursty flows in magnetosphere influence ionosphere

In Earth\textquoterights plasma sheet\textemdasha region of dense ionized gas that lies around the equatorial plane and extends into the magnetotail\textemdashplasma 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 ...

Balcerak, Ernie;

YEAR: 2014     DOI: 10.1002/eost.v95.2810.1002/2014EO280019

Bubbles; Bursty bulk flows; Entropy

Direct Observation of Radiation-Belt Electron Acceleration from Electron-Volt Energies to Megavolts by Nonlinear Whistlers

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\textquoterights 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 becom ...

Mozer, S.; Agapitov, O.; Krasnoselskikh, V.; Lejosne, S.; Reeves, D.; Roth, I.;

YEAR: 2014     DOI: 10.1103/PhysRevLett.113.035001

Van Allen Probes

Direct Observation of Radiation-Belt Electron Acceleration from Electron-Volt Energies to Megavolts by Nonlinear Whistlers

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\textquoterights 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 becom ...

Mozer, F.; Agapitov, O.; Krasnoselskikh, V.; Lejosne, S.; Reeves, G.; Roth, I.;

YEAR: 2014     DOI: 10.1103/PhysRevLett.113.035001

Estimates of the power per mode number of broadband ULF waves at geosynchronous orbit

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\textquoteright 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 o ...

Sarris, T.;

YEAR: 2014     DOI: 10.1002/2013JA019238

Magnetosphere; mode number; radial diffusion; Radiation belts; ULF waves; ultralow frequency

Evolution of nightside subauroral proton aurora caused by transient plasma sheet flows

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 bounda ...

Nishimura, Y.; Bortnik, J.; Li, W.; Lyons, L.; Donovan, E.; Angelopoulos, V.; Mende, S.;

YEAR: 2014     DOI: 10.1002/2014JA020029

EMIC waves; plasma sheet flow burst; plasmasphere; proton aurora; THEMIS ASI; THEMIS satellite

Magnetopause structure favorable for radiation belt electron loss

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 calculation ...

Kim, Kyung-Chan; Lee, Dae-Young;

YEAR: 2014     DOI: 10.1002/2014JA019880

magnetopause shadowing; relativistic electron loss; test particle orbit calculation

A novel technique to construct the global distribution of whistler mode chorus wave intensity using low-altitude POES electron data

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 tech ...

Ni, Binbin; Li, Wen; Thorne, Richard; Bortnik, Jacob; Green, Janet; Kletzing, Craig; Kurth, William; Hospodarsky, George; Pich, Maria;

YEAR: 2014     DOI: 10.1002/jgra.v119.710.1002/2014JA019935

electron precipitation; global wave distribution; magnetospheric chorus; physics-based technique; wave resonant scattering

The Energetic Particle Detector (EPD) Investigation and the Energetic Ion Spectrometer (EIS) for the Magnetospheric Multiscale (MMS) Mission

The Energetic Particle Detector (EPD) Investigation is one of 5 fields-and-particles investigations on the Magnetospheric Multiscale (MMS) mission. MMS comprises 4 spacecraft flying in close formation in highly elliptical, near-Earth-equatorial orbits targeting understanding of the fundamental physics of the important physical process called magnetic reconnection using Earth\textquoterights magnetosphere as a plasma laboratory. EPD comprises two sensor types, the Energetic Ion Spectrometer (EIS) with one instrument on each o ...

Mauk, B.; Blake, J.; Baker, D.; Clemmons, J.; Reeves, G.; Spence, H.; Jaskulek, S.; Schlemm, C.; Brown, L.; Cooper, S.; Craft, J.; Fennell, J.; Gurnee, R.; Hammock, C.; Hayes, J.; Hill, P.; Ho, G.; Hutcheson, J.; Jacques, A.; Kerem, S.; Mitchell, D.; Nelson, K.; Paschalidis, N.; Rossano, E.; Stokes, M.; Westlake, J.;

YEAR: 2014     DOI: 10.1007/s11214-014-0055-5

Magnetic reconnection; Magnetosphere; Magnetospheric multiscale; NASA mission; Particle acceleration; Space plasma

Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013

We report the wave observations, associated plasma measurements, and linear theory testing of electromagnetic ion cyclotron (EMIC) wave events observed by the Van Allen Probes on 28 April 2013. The wave events are detected in their generation regions as three individual events in two consecutive orbits of Van Allen Probe-A, while the other spacecraft, B, does not detect any significant EMIC wave activity during this period. Three overlapping H+ populations are observed around the plasmapause when the waves are excited. The d ...

Zhang, J.-C.; Saikin, A.; Kistler, L.; Smith, C.; Spence, H.; Mouikis, C.; Torbert, R.; Larsen, B.; Reeves, G.; Skoug, R.; Funsten, H.; Kurth, W.; Kletzing, C.; Allen, R.; Jordanova, V.;

YEAR: 2014     DOI: 10.1002/2014GL060621

Van Allen Probes

Intense duskside lower band chorus waves observed by Van Allen Probes: Generation and potential acceleration effect on radiation belt electrons

Local acceleration driven by whistler mode chorus waves largely accounts for the enhancement of radiation belt relativistic electron fluxes, whose favored region is usually considered to be the plasmatrough with magnetic local time approximately from midnight through dawn to noon. On 2 October 2013, the Van Allen Probes recorded a rarely reported event of intense duskside lower band chorus waves (with power spectral density up to 10-3nT2/Hz) in the low-latitude region outside of L=5. Such chorus waves are found to be generat ...

Su, Zhenpeng; Zhu, Hui; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; He, Zhaoguo; Shen, Chao; Shen, Chenglong; Wang, C.; Liu, Rui; Zhang, Min; Wang, Shui; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; Baker, D.; Wygant, J.;

YEAR: 2014     DOI: 10.1002/jgra.v119.610.1002/2014JA019919

Van Allen Probes

Large anisotropies of >60 MeV protons throughout the inner belt observed with the Van Allen Probes mission

We report large directional anisotropies of >60 MeV protons using instrumentation on the Van Allen Probes. The combination of a spinning satellite and measurements from the Relativistic Proton Spectrometer instruments that are insensitive to protons outside the instrument field of view together yield a new look at proton radial gradients. The relatively large proton gyroradius at 60 MeV couples with the radial gradients to produce large (maximum ~10:1) flux anisotropies depending on (i) whether the proton guiding center was ...

Mazur, J.; O\textquoterightBrien, T.; Looper, M.; Blake, J.;

YEAR: 2014     DOI: 10.1002/grl.v41.1110.1002/2014GL060029

Van Allen Probes

Radiation belt electron acceleration by chorus waves during the 17 March 2013 storm

Local acceleration driven by whistler-mode chorus waves is fundamentally important for accelerating seed electron populations to highly relativistic energies in the outer radiation belt. In this study, we quantitatively evaluate chorus-driven electron acceleration during the 17 March 2013 storm, when the Van Allen Probes observed very rapid electron acceleration up to several MeV within ~12 hours. A clear radial peak in electron phase space density (PSD) observed near L* ~4 indicates that an internal local acceleration proce ...

Li, W.; Thorne, R.; Ma, Q.; Ni, B.; Bortnik, J.; Baker, D.; Spence, H.; Reeves, G.; Kanekal, S.; Green, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Blake, J.; Fennell, J.; Claudepierre, S.;

YEAR: 2014     DOI: 10.1002/jgra.v119.610.1002/2014JA019945

Van Allen Probes

Chorus acceleration of radiation belt relativistic electrons during March 2013 geomagnetic storm

The recent launching of Van Allen probes provides an unprecedent opportunity to investigate variations of the radiation belt relativistic electrons. During the 17\textendash19 March 2013 storm, the Van Allen probes simultaneously detected strong chorus waves and substantial increases in fluxes of relativistic (2 - 4.5 MeV) electrons around L = 4.5. Chorus waves occurred within the lower band 0.1\textendash0.5fce (the electron equatorial gyrofrequency), with a peak spectral density \~10-4 nT2/Hz. Correspondingly, relativistic ...

Xiao, Fuliang; Yang, Chang; He, Zhaoguo; Su, Zhenpeng; Zhou, Qinghua; He, Yihua; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; Baker, D.; Wygant, J.;

YEAR: 2014     DOI: 10.1002/2014JA019822

Van Allen Probes

A numerical study of chorus generation and the related variation of wave intensity using the DAWN code

Chorus waves play an important role in energetic electron dynamics in the inner magnetosphere. In this work, we present a new hybrid code, DAWN, to simulate the generation of chorus waves. The DAWN code is unique in that it models cold electrons using linearized fluid equations and hot electrons using particle-in-cell techniques. The simplified fluid equations can be solved with robust and simple algorithms. We demonstrate that discrete chorus elements can be generated using the code. Waveforms of the generated element show ...

Tao, X.;

YEAR: 2014     DOI: 10.1002/2014JA019820

chorus excitation; plasma simulation; whistler intensity modulation

In situ observations of Pc1 pearl pulsations by the Van Allen Probes

We present in situ observations of Pc1 pearl pulsations using the Van Allen Probes. These waves are often observed using ground-based magnetometers, but are rarely observed by orbiting satellites. With the Van Allen Probes, we have seen at least 14 different pearl pulsation events during the first year of operations. These new in situ measurements allow us to identify the wave classification based on local magnetic field conditions. Additionally, by using two spacecraft, we are able to observe temporal changes in the region ...

Paulson, K.; Smith, C.; Lessard, M.; Engebretson, M.; Torbert, R.; Kletzing, C.;

YEAR: 2014     DOI: 10.1002/2013GL059187

Van Allen Probes

Inner belt and slot region electron lifetimes and energization rates based on AKEBONO statistics of whistler waves

Global statistics of the amplitude distributions of hiss, lightning-generated, and other whistler mode waves from terrestrial VLF transmitters have been obtained from the EXOS-D (Akebono) satellite in the Earth\textquoterights plasmasphere and fitted as functions of L and latitude for two geomagnetic activity ranges (Kp<3 and Kp>3). In particular, the present study focuses on the inner zone L∈[1.4,2] where reliable in situ measurements were lacking. Such statistics are critically needed for an accurate assessment of the ro ...

Agapitov, O.; Artemyev, A.; Mourenas, D.; Kasahara, Y.; Krasnoselskikh, V.;

YEAR: 2014     DOI: 10.1002/jgra.v119.410.1002/2014JA019886

Inner radiation belt; Van Allen Probes; Wave-particle interaction

Journal Special Collection Explores Early Results From the Van Allen Probes Mission

The processes governing the charged particle populations in the radiation belts encircling Earth have been the subject of intense interest and increasing concern since their discovery by James Van Allen and his team more than 50 years ago [Baker et al., 2013]. Intense interest continues because we still do not know how the various processes work in concert to enhance, remove, and transport particle radiation. Concern is ongoing because the Van Allen radiation belts pose hazards to astronauts and our ever-growing fleet of spa ...

Mauk, Barry; Sibeck, David; Kessel, Ramona;

YEAR: 2014     DOI: 10.1002/eost.v95.1310.1002/2014EO130007

Van Allen Probes

The main pillar: Assessment of space weather observational asset performance supporting nowcasting, forecasting, and research to operations

Space weather forecasting critically depends upon availability of timely and reliable observational data. It is therefore particularly important to understand how existing and newly planned observational assets perform during periods of severe space weather. Extreme space weather creates challenging conditions under which instrumentation and spacecraft may be impeded or in which parameters reach values that are outside the nominal observational range. This paper analyzes existing and upcoming observational capabilities for f ...

Posner, A.; Hesse, M.; St. Cyr, O.;

YEAR: 2014     DOI: 10.1002/swe.v12.410.1002/2013SW001007

Assessment; Space Hardware; SWx Forecasting; Van Allen Probes

Peculiar pitch angle distribution of relativistic electrons in the inner radiation belt and slot region

The relativistic electrons in the inner radiation belt have received little attention in the past due to sparse measurements and unforgiving contamination from the inner belt protons. The high-quality measurements of the Magnetic Electron Ion Spectrometer instrument onboard Van Allen Probes provide a great opportunity to investigate the dynamics of relativistic electrons in the low L region. In this letter, we report the newly unveiled pitch angle distribution (PAD) of the energetic electrons with minima at 90\textdegree nea ...

Zhao, H.; Li, X.; Blake, J.; Fennell, J.; Claudepierre, S.; Baker, D.; Jaynes, A.; Malaspina, D.; Kanekal, S.;

YEAR: 2014     DOI: 10.1002/2014GL059725

Van Allen Probes

Quantifying the radiation belt seed population in the 17 March 2013 electron acceleration event

We present phase space density (PSD) observations using data from the Magnetic Electron Ion Spectrometer instrument on the Van Allen Probes for the 17 March 2013 electron acceleration event. We confirm previous results and quantify how PSD gradients depend on the first adiabatic invariant. We find a systematic difference between the lower-energy electrons (1 MeV with a source region within the radiation belts. Our observations show that the source p ...

Boyd, A.; Spence, H.; Claudepierre, S.; Fennell, J.; Blake, J.; Baker, D.; Reeves, G.; Turner, D.;

YEAR: 2014     DOI: 10.1002/2014GL059626

Van Allen Probes

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