Found 1095 entries in the Bibliography.

Showing entries from 801 through 850


Empirical modeling of the storm-time innermost magnetosphere using Van Allen Probes and THEMIS data: Eastward and banana currents

The structure of storm-time currents in the inner magnetosphere, including its innermost region inside 4RE, is studied for the first time using a modification of the empirical geomagnetic field model TS07D and new data from Van Allen Probes and THEMIS missions. It is shown that the model, which uses basis-function expansions instead of ad hoc current modules to approximate the magnetic field, consistently improves its resolution and magnetic field reconstruction with the increase of the number of basis functions and resolves ...

Stephens, G.; Sitnov, M.; . Y. Ukhorskiy, A; Roelof, E.; Tsyganenko, N.; Le, G.;

YEAR: 2015     DOI: 10.1002/2015JA021700

eastward current; empirical geomagnetic field; magnetic storm; ring current; Van Allen Probes


Van Allen Probe Observations of Periodic Rising Frequencies of the Fast Magnetosonic Mode

Near simultaneous periodic dispersive features of fast magnetosonic mode emissions are observed by both Van Allen Probes spacecraft while separated in magnetic local time by ~5 hours: Probe A at 15 and Probe B at 9\textendash11 hours. Both spacecraft see similar frequency features, characterized by a periodic repetition at ~180 s. Each repetition is characterized by a rising frequency. Since no modulation is observed in the proton shell distribution, the plasma density, or in the background magnetic field at either spacecraf ...

Boardsen, S.; Hospodarsky, G.; Kletzing, C.; Pfaff, R.; Kurth, W.; Wygant, J.; MacDonald, E.;

YEAR: 2014     DOI: 10.1002/2014GL062020

Fast Magnetosonic Waves; Inner Dayside Magnetosphere; Periodic-Dispersive Features; Van Allen Probes

Wave normal angles of whistler-mode chorus rising and falling tones

We present a study of wave normal angles (θk) of whistler mode chorus emission as observed by Time History of Events and Macroscale Interactions during Substorms (THEMIS) during the year 2008. The three inner THEMIS satellites THA, THD, and THE usually orbit Earth close to the dipole magnetic equator (\textpm20\textdegree), covering a large range of L shells from the plasmasphere out to the magnetopause. Waveform measurements of electric and magnetic fields enable a detailed polarization analysis of chorus below 4 kHz. When ...

Taubenschuss, Ulrich; Khotyaintsev, Yuri; ik, Ondrej; Vaivads, Andris; Cully, Christopher; Le Contel, Olivier; Angelopoulos, Vassilis;

YEAR: 2014     DOI: 10.1002/2014JA020575

Chorus; wave normal

The activity and radial dependence of anomalous diffusion by pitch-angle scattering on split magnetic drift shells

Asymmetries in the magnetospheric magnetic field produce drift shell splitting, which causes the radial (drift shell) invariant to sometimes depend on pitch angle. Where drift shell splitting is significant, pitch angle scattering leads to diffusion in all three invariants of the particle\textquoterights motion, including cross diffusion. We examine the magnitude of drift shell splitting-related anomalous diffusion for outer zone electrons compared to conventional diffusion in the absence of drift shell splitting. We assume ...

O\textquoterightBrien, T.P.;

YEAR: 2014     DOI: 10.1002/2014JA020422

Diffusion; Drift shell splitting; Radiation belt

Evolution of relativistic outer belt electrons during an extended quiescent period

To effectively study steady loss due to hiss-driven precipitation of relativistic electrons in the outer radiation belt, it is useful to isolate this loss by studying a time of relatively quiet geomagnetic activity. We present a case of initial enhancement and slow, steady decay of 700 keV - 2 MeV electron populations in the outer radiation belt during an extended quiescent period from ~15 December 2012 - 13 January 2013. We incorporate particle measurements from a constellation of satellites, including the Colorado Student ...

Jaynes, A.; Li, X.; Schiller, Q.; Blum, L.; Tu, W.; Turner, D.; Ni, B.; Bortnik, J.; Baker, D.; Kanekal, S.; Blake, J.; Wygant, J.;

YEAR: 2014     DOI: 10.1002/2014JA020125

electron lifetime; hiss waves; pitch angle scattering; precipitation loss; Radiation belts; Van Allen Probes

Externally driven plasmaspheric ULF waves observed by the Van Allen Probes

We analyze data acquired by the Van Allen Probes on 8 November 2012, during a period of extended low geomagnetic activity, to gain new insight into plasmaspheric ultra-low-frequency (ULF) waves. The waves exhibited strong spectral power in the 5\textendash40 mHzband and included multiharmonic toroidal waves visible up to the 11th harmonic, unprecedented in the plasmasphere. During this wave activity, the interplanetary magnetic field cone angle was small, suggesting that the waves were driven by broadband compressional ULF w ...

Takahashi, Kazue; Denton, Richard; Kurth, William; Kletzing, Craig; Wygant, John; Bonnell, John; Dai, Lei; Min, Kyungguk; Smith, Charles; MacDowall, Robert;

YEAR: 2014     DOI: 10.1002/2014JA020373

multispacecraft observation; Van Allen Probes; plasmasphere; ULF waves

Fine structure of plasmaspheric hiss

Plasmaspheric hiss has been widely regarded as a broadband, structureless, incoherent emission. In this study, by examining burst-mode vector waveform data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument on the Van Allen Probes mission, we show that plasmaspheric hiss is a coherent emission with complex fine structure. Specifically, plasmaspheric hiss appears as discrete rising tone and falling tone elements. Our study comprises the analysis of two one-hour samples within whi ...

Summers, Danny; Omura, Yoshiharu; Nakamura, Satoko; Kletzing, Craig;

YEAR: 2014     DOI: 10.1002/2014JA020437

Plasmaspheric Hiss; Van Allen Probes; whistler mode waves

Investigation of EMIC wave scattering as the cause for the BARREL January 17, 2013 relativistic electron precipitation event: a quantitative comparison of simulation with observations

Electromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the BARREL balloons, and was magnetically mapped close to GOES-13. We simulate the relativistic electron pitch-angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES-13 and the Van Allen Probes. We ...

Li, Zan; Millan, Robyn; Hudson, Mary; Woodger, Leslie; Smith, David; Chen, Yue; Friedel, Reiner; Rodriguez, Juan; Engebretson, Mark; Goldstein, Jerry; Fennell, Joseph; Spence, Harlan;

YEAR: 2014     DOI: 10.1002/2014GL062273

BARREL; EMIC waves; GOES; pitch angle diffusion; RBSP; relativistic electron precipitation; Van Allen Probes

Quantifying the relative contributions of substorm injections and chorus waves to the rapid outward extension of electron radiation belt

We study the rapid outward extension of the electron radiation belt on a timescale of several hours during three events observed by RBSP and THEMIS satellites, and particularly quantify the contributions of substorm injections and chorus waves to the electron flux enhancement near the outer boundary of radiation belt. A comprehensive analysis including both observations and simulations is performed for the first event on 26 May 2013. The outer boundary of electron radiation belt moved from L = 5.5 to L > 6.07 over about 6 ho ...

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

YEAR: 2014     DOI: 10.1002/2014JA020709

Chorus wave; Electron acceleration; Radiation belt; substorm injection; Van Allen Probes; Wave-particle interaction

Source and structure of bursty hot electron enhancements in the tail magnetosheath: Simultaneous two-probe observation by ARTEMIS

Bursty enhancements of hot electrons (≳0.5 keV) with duration of minutes sometimes occur in the tail magnetosheath. In this study we used the unique simultaneous measurements from the two Acceleration Reconnection Turbulence and Electrodynamics of Moon\textquoterights Interaction with the Sun probes to investigate the likely sources, spatial structures, and responsible processes for these hot electron enhancements. The enhancements can be seen at any distance across the magnetosheath, but those closer to the magnetopause a ...

Wang, Chih-Ping; Xing, Xiaoyan; Nakamura, T.; Lyons, Larry; Angelopoulos, Vassilis;

YEAR: 2014     DOI: 10.1002/2014JA020603

ARTEMIS; hot electrons; magnetosheath

Trapping waves in Earth\textquoterights plasmasphere

Earth\textquoterights magnetic field traps donut-shaped bands of radiation in a belt around the planet that react to solar eruptions by growing and shrinking. The Van Allen belts consist of two rings filled with particles from the solar wind and cosmic rays. Within the outer ring of the Van Allen belt sits the plasmasphere, which is the innermost part of the planet\textquoterights magnetic field and home to low-energy charged particles.

Betz, Eric;

YEAR: 2014     DOI: 10.1002/2014EO490016

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

Approximate analytical solutions for the trapped electron distribution due to quasi-linear diffusion by whistler-mode waves

The distribution of trapped energetic electrons inside the Earth\textquoterights radiation belts is the focus of intense studies aiming at better describing the evolution of the space environment in the presence of various disturbances induced by the solar wind or by an enhanced lightning activity. Such studies are usually performed by means of comparisons with full numerical simulations solving the Fokker-Planck quasi-linear diffusion equation for the particle distribution function. Here, we present for the first time appro ...

Mourenas, D.; Artemyev, A.; Agapitov, O.V.; Krasnoselskikh, V.; Li, W.;

YEAR: 2014     DOI: 10.1002/2014JA020443

electron distribution; pitch-angle distribution; Radiation belt

Characteristics of pitch angle distributions of 100 s keV electrons in the slot region and inner radiation belt

The pitch angle distribution (PAD) of energetic electrons in the slot region and inner radiation belt received little attention in the past decades due to the lack of quality measurements. Using the state-of-art pitch-angle-resolved data from the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard the Van Allen Probes, a detailed analysis of 100 s keV electron PADs below L = 4 is performed, in which the PADs is categorized into three types: normal (flux peaking at 90o), cap (exceedingly peaking narrowly around 90o ...

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

YEAR: 2014     DOI: 10.1002/2014JA020386

energetic electrons; Inner radiation belt; Pitch angle distribution; plasmasphere; Slot region; Van Allen Probes; Wave-particle interaction

Characteristics of precipitating energetic electron fluxes relative to the plasmapause during geomagnetic storms

n this study we investigate the link between precipitating electrons from the Van Allen radiation belts and the dynamical plasmapause. We consider electron precipitation observations from the Polar Orbiting Environmental Satellite (POES) constellation during geomagnetic storms. Superposed epoch analysis is performed on precipitating electron observations for the 13 year period of 1999 to 2012 in two magnetic local time (MLT) sectors, morning and afternoon. We assume that the precipitation is due to wave-particle interactions ...

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

YEAR: 2014     DOI: 10.1002/2014JA020446

energetic electron precipitation; Plasmapause; POES

Characterization of the energy-dependent response of riometer absorption

Ground based riometers provide an inexpensive means to continuously remote sense the precipitation of electrons in the dynamic auroral region of Earth\textquoterights ionosphere. The energy-dependent relationship between riometer absorption and precipitating electrons is thus of great importance for understanding the loss of electrons from the Earth\textquoterights magnetosphere. In this study, statistical and event-based analyses are applied to determine the energy of electrons to which riometers chiefly respond. Time-lagge ...

Kellerman, A.; . Y. Shprits, Y; Makarevich, R.; Spanswick, E.; Donovan, E.; Reeves, G.;

YEAR: 2014     DOI: 10.1002/2014JA020027

cosmic noise absorption; electron energy; particle modeling; Radiation belts; riometer; electron precipitation

Comparative Investigation of the Energetic Ion Spectra Comprising the Magnetospheric Ring Currents of the Solar System

Investigated here are factors that control the intensities and shapes of energetic ion spectra that make up the ring current populations of the strongly magnetized planets of the solar system, specifically those of Earth, Jupiter, Saturn, Uranus, and Neptune. Following a previous and similar comparative investigation of radiation belt electrons, we here turn our attention to ions. Specifically, we examine the possible role of the differential ion Kennel-Petschek limit, as moderated by Electromagnetic Ion Cyclotron (EMIC) wav ...

Mauk, B.;

YEAR: 2014     DOI: 10.1002/2014JA020392

Ion Spectra; Magnetic Storms; Planetary magnetospheres; ring current; Van Allen Probes

Electron lifetimes from narrowband wave-particle interactions within the plasmasphere

This paper is devoted to the systematic study of electron lifetimes from narrowband wave-particle interactions within the plasmasphere. It relies on a new formulation of the bounce-averaged quasi-linear pitch angle diffusion coefficients parameterized by a single frequency, ω, and wave normal angle, θ. We first show that the diffusion coefficients scale with ω/Ωce, where Ωce is the equatorial electron gyrofrequency, and that maximal pitch angle diffusion occurs along the line α0 = π/2\textendashθ, where α0 is the eq ...

Ripoll, J.-F.; Albert, J.; Cunningham, G.;

YEAR: 2014     DOI: 10.1002/2014JA020217

DSX; electron; narrowband; plasmasphere; wave-particle interactions

Electron losses from the radiation belts caused by EMIC waves

Electromagnetic Ion Cyclotron (EMIC) waves cause electron loss in the radiation belts by resonating with high-energy electrons at energies greater than about 500 keV. However, their effectiveness has not been fully quantified. Here we determine the effectiveness of EMIC waves by using wave data from the fluxgate magnetometer on CRRES to calculate bounce-averaged pitch angle and energy diffusion rates for L*=3.5\textendash7 for five levels of Kp between 12 and 18 MLT. To determine the electron loss, EMIC diffusion rates were ...

Kersten, Tobias; Horne, Richard; Glauert, Sarah; Meredith, Nigel; Fraser, Brian; Grew, Russell;

YEAR: 2014     DOI: 10.1002/2014JA020366

electron losses; EMIC waves

Excitation of nightside magnetosonic waves observed by Van Allen Probes

During the recovery phase of the geomagnetic storm on 30-31 March 2013, Van Allen Probe A detected enhanced magnetosonic (MS) waves in a broad range of L =1.8-4.7 and MLT =17-22 h, with a frequency range ~10-100 Hz. In the meanwhile, distinct proton ring distributions with peaks at energies of ~10 keV, were also observed in L =3.2-4.6 and L =5.0-5.6. Using a subtracted bi-Maxwellian distribution to model the observed proton ring distribution, we perform three dimensional ray tracing to investigate the instability, propagatio ...

Zhou, Qinghua; Xiao, Fuliang; Yang, Chang; Liu, Si; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; Baker, D.; Wygant, J.;

YEAR: 2014     DOI: 10.1002/2014JA020481

magnetosonic wave; RBSP results; Van Allen Probes; Wave-particle interaction

Feasibility study of astronaut standardized career dose limits in LEO and the outlook for BLEO

Cosmic Study Group SG 3.19/1.10 was established in February 2013 under the aegis of the International Academy of Astronautics to consider and compare the dose limits adopted by various space agencies for astronauts in Low Earth Orbit. A preliminary definition of the limits that might later be adopted by crews exploring Beyond Low Earth Orbit was, in addition, to be made. The present paper presents preliminary results of the study reported at a Symposium held in Turin by the Academy in July 2013. First, an account is provided ...

McKenna-Lawlor, Susan;

YEAR: 2014     DOI: 10.1016/j.actaastro.2014.07.011

Dose limits; Galactic Cosmic Radiation; Solar Energetic Particles

First observation of rising-tone magnetosonic waves

Magnetosonic (MS) waves are linearly polarized emissions confined near the magnetic equator with wave normal angle near 90\textdegree and frequency below the lower hybrid frequency. Such waves, also termed equatorial noise, were traditionally known to be \textquotedbllefttemporally continuous\textquotedblright in their time-frequency spectrogram. Here we show for the first time that MS waves actually have discrete wave elements with rising-tone features in their spectrogram. The frequency sweep rate of MS waves, ~1 Hz/s, is ...

Fu, H.; Cao, J.; Zhima, Z.; Khotyaintsev, Y.; Angelopoulos, V.; ik, O.; Omura, Y.; Taubenschuss, U.; Chen, L.; . Y. Huang, S;

YEAR: 2014     DOI: 10.1002/grl.v41.2110.1002/2014GL061867

discrete; frequency sweep rate; magnetosonic wave; nonlinear wave-particle interaction; Plasmapause; rising tone

An impenetrable barrier to ultrarelativistic electrons in the Van Allen radiation belts

Early observations1, 2 indicated that the Earth\textquoterights Van Allen radiation belts could be separated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. Subsequent studies3, 4 showed that electrons of moderate energy (less than about one megaelectronvolt) often populate both zones, with a deep \textquoteleftslot\textquoteright region largely devoid of particles between them. There is a region of dense cold plasma around the Earth known as the plasmasphere, the out ...

Baker, D.; Jaynes, A.; Hoxie, V.; Thorne, R.; Foster, J.; Li, X.; Fennell, J.; Wygant, J.; Kanekal, S.; Erickson, P.; Kurth, W.; Li, W.; Ma, Q.; Schiller, Q.; Blum, L.; Malaspina, D.; Gerrard, A.; Lanzerotti, L.;

YEAR: 2014     DOI: 10.1038/nature13956

Magnetospheric physics; ultrarelativistic electrons; Van Allen Belts; Van Allen Probes

Initial Measurements of O-ion and He-ion Decay Rates Observed from the Van Allen Probes RBSPICE Instrument

H-ion (~45-keV to ~600-keV), He-ion (~65-keV to ~520-keV), and O-ion (~140-keV to ~1130-keV) integral flux measurements, from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft B, are reported. These abundance data form a cohesive picture of ring current ions during the first nine months of measurements. Furthermore, the data presented herein are used to show injection characteristics via the He-ion/H-ion abundance ratio and the O-ion/H-ion abundance ratio. O ...

Gerrard, Andrew; Lanzerotti, Louis; Gkioulidou, Matina; Mitchell, Donald; Manweiler, Jerry; Bortnik, Jacob; Keika, Kunihiro;

YEAR: 2014     DOI: 10.1002/2014JA020374

inner magnetosphere; ion decay rates; Spacecraft measurements; Van Allen Probes

On long decays of electrons in the vicinity of the slot region observed by HEO3

Long decay periods of electron counts, which follow abrupt rises and last from weeks to months, have been observed by the HEO3 spacecraft in the vicinity of the slot region between the years 1998 and 2007. During the most stable decay periods as selected, e-folding timescales are extracted and statistically analyzed from observations as a function of L-shell and electron energy. A challenge is to reproduce the observed timescales from simulations of pitch angle diffusion by three acting waves\textendashthe plasmaspheric hiss ...

Ripoll, J.-F.; Chen, Y.; Fennell, J.; Friedel, R.;

YEAR: 2014     DOI: 10.1002/2014JA020449

electron; HEO; Slot region

Meeting Report: Solar Energetic Particle Measurements Intercalibration Workshop, 11 April 2014, Boulder, Colorado

Following the conclusion of the 2014 Space Weather Week in Boulder, Colorado, the NOAA National Geophysical Data Center and Space Weather Prediction Center cohosted a 1 day workshop on the intercalibration of solar energetic particle (SEP) measurements. The overall purpose of this workshop was to discuss the intercalibration of SEP measurements from different instruments and different spacecraft, to foster new cooperative intercalibration efforts, and to identify a path forward for establishing a set of intercalibration guid ...

Rodriguez, Juan; Onsager, Terrance; Heynderickx, Daniel; Jiggens, Piers;

YEAR: 2014     DOI: 10.1002/swe.v12.1110.1002/2014SW001134

cross calibration; interoperability; Solar Energetic Particles

Modeling radiation belt electron acceleration by ULF fast mode waves, launched by solar wind dynamic pressure fluctuations

We investigate the magnetospheric MHD and energetic electron response to a Storm Sudden Commencement (SSC) and subsequent magnetopause buffeting, focusing on an interval following an SSC event on 25 November 2001. We find that the electron flux signatures observed by LANL, Cluster, and GOES spacecraft during this event can largely be reproduced using an advective kinetic model for electron phase space density, using externally prescribed electromagnetic field inputs, (herein described as a \textquotedbllefttest-kinetic model ...

Degeling, A.; Rankin, R.; Zong, Q.-G.;

YEAR: 2014     DOI: 10.1002/2013JA019672

adiabatic electron transport; magnetopause buffeting; Radiation belts; ULF waves

Observations and modeling of EMIC wave properties in the presence of multiple ion species as function of magnetic local time

Electromagnetic ion cyclotron (EMIC) wave generation and propagation in Earth\textquoterights magnetosphere depend on readily measurable hot (a few to tens of keV) plasma sheet ions, elusive plasmaspheric or ionospheric cold (sub-eV to a few eV) ions, and partially heated warm ions (tens to hundreds of eV). Previous work has assumed all low-energy ions are cold and not considered possible effects of warm ions. Using measurements by multiple Time History of Events and Macroscale Interactions during Substorms spacecraft, we an ...

Lee, Justin; Angelopoulos, Vassilis;

YEAR: 2014     DOI: 10.1002/2014JA020469

EMIC waves; ion composition; ion cyclotron waves; low-energy ions; THEMIS; warm plasma effects

Radial diffusion simulations of the 20 September 2007 radiation belt dropout

This is a study of a dropout of radiation belt electrons, associated with an isolated solar wind density pulse on 20 September 2007, as seen by the solid-state telescopes (SST) detectors on THEMIS (Time History of Events and Macroscale Interactions during Substorms). Omnidirectional fluxes were converted to phase space density at constant invariants M = 700 MeV G-1 and K = 0.014 RE G1/2, with the assumption of local pitch angle α ≈ 80\textdegree and using the T04 magnetic field model. The last closed drift shell, which wa ...

Albert, J.;

YEAR: 2014     DOI: 10.5194/angeo-32-925-2014

radial diffusion

Statistical results describing the bandwidth and coherence coefficient of whistler mode waves using THEMIS waveform data

The bandwidths and coherence coefficients of lower band whistler mode waves are analyzed using Time History of Events and Macroscale Interactions during Substorms (THEMIS) waveform data for rising tones, falling tones, and hiss-like emissions separately. We also evaluate their dependences on the spatial location, electron density, the ratio of plasma frequency to local electron gyrofrequency (fpe/fce), and the wave amplitude. Our results show that the bandwidth normalized by the local electron gyrofrequency (fce) of rising a ...

Gao, X.; Li, W.; Thorne, R.; Bortnik, J.; Angelopoulos, V.; Lu, Q.; Tao, X.; Wang, S.;

YEAR: 2014     DOI: 10.1002/2014JA020158

bandwidth; coherence coefficient; nonlinear; quasi-linear; THEMIS; whistler mode waves

A ULF wave driver of ring current energization

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 w ...

Murphy, Kyle; Mann, Ian; Ozeke, Louis;

YEAR: 2014     DOI: 10.1002/grl.v41.1910.1002/2014GL061253

Dst; radial diffusion; ring current dynamics; ULF waves; wave particle interactions

An unusual long-lived relativistic electron enhancement event excited by sequential CMEs

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 \texttimes 102 cm-2\textperiodcenteredsr-1\textperiodcentereds-1 to 3.5 \texttimes 104 cm-2\textperiodcenteredsr-1\textperiodcentereds-1, the region of enhanced fluxes extended from L = 3.5-6.5 to ...

Yang, Xiao; Zhu, Guang; Zhang, Xiao; Sun, Yue; Liang, Jin; Wei, Xin;

YEAR: 2014     DOI: 10.1002/2014JA019797

Geomagnetic storm/substorm; Interplanetary magnetic field; Plasmapause; Relativistic electron; Solar wind

Whistler Anisotropy Instabilities as the Source of Banded Chorus: Van Allen Probes Observations and Particle-in-Cell Simulations

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 ...

Fu, Xiangrong; Cowee, Misa; Friedel, Reinhard; Funsten, Herbert; Gary, Peter; Hospodarsky, George; Kletzing, Craig; Kurth, William; Larsen, Brian; Liu, Kaijun; MacDonald, Elizabeth; Min, Kyungguk; Reeves, Geoffrey; Skoug, Ruth; Winske, Dan;

YEAR: 2014     DOI: 10.1002/2014JA020364

Chorus; HOPE; particle-in-cell simulation; Van Allen Probes

Equivalent Circuit Model for the Electric Field Sensitivity of a Magnetic Search Coil of Space Plasma

Magnetic search coils (MSCs) are sensitive to both magnetic and electric fields, but detecting electric fields is unnecessary for magnetic observations of plasma waves. However, it is important to evaluate both sensitivities for different geometries and electrostatic shields to avoid electric field pickup. An equivalent circuit model for the electric field sensitivity of an MSC in a collisionless isotropic cold plasma is developed here using electrical coupling through a sheath capacitance. That sensitivity is defined by a r ...

Ozaki, Mitsunori; Yagitani, Satoshi; Takahashi, Ken; Imachi, Tomohiko; Koji, Hiroki; Higashi, Ryoichi;

YEAR: 2014     DOI: 10.1109/JSEN.2014.2365495

electric field sensitivity; Magnetic search coils; sheath impedance; space plasmas

The Evolving Space Weather System - Van Allen Probes Contribution

The overarching goal and purpose of the study of space weather is clear - to understand and address the issues caused by solar disturbances on humans and technological systems. Space weather has evolved in the past few decades from a collection of concerned agencies and researchers to a critical function of the National Weather Service of NOAA. The general effects have also evolved from the well-known telegraph disruptions of the mid-1800\textquoterights to modern day disturbances of the electric power grid, communications a ...

Zanetti, L.; Mauk, B.; Fox, N.J.; Barnes, R.J.; Weiss, M.; Sotirelis, T.S.; Raouafi, N.-E.; Kessel, R.; Becker, H.;

YEAR: 2014     DOI: 10.1002/2014SW001108

Radiation belts; Van Allen Probes

Interactions of energetic electrons with ULF waves triggered by interplanetary shock: Van Allen Probes observations in the magnetotail

We present in situ observations of a shock-induced substorm-like event on 13 April 2013 observed by the newly launched Van Allen twin probes. Substorm-like electron injections with energy of 30\textendash500 keV were observed in the region from L\~5.2 to 5.5 immediately after the shock arrival (followed by energetic electron drift echoes). Meanwhile, the electron flux was clearly and strongly varying on the ULF wave time scale. It is found that both toroidal and poloidal mode ULF waves with a period of 150 s emerged followin ...

Hao, Y.; Zong, Q.-G.; Wang, Y.; Zhou, X.-Z.; Zhang, Hui; . Y. Fu, S; . Y. Pu, Z; Spence, H.; Blake, J.; Bonnell, J.; Wygant, J.; Kletzing, C.;

YEAR: 2014     DOI: 10.1002/2014JA020023

energetic particles; interplanetary shock; magnetotail ULF wave; poloidal and toroidal mode; Van Allen Probes; wave-particle interactions

Modeling cross L shell impacts of magnetopause shadowing and ULF wave radial diffusion in the Van Allen belts

We present simulations of the outer electron radiation belt using a new ULF wave-driven radial diffusion model, including empirical representations of loss due to chorus and plasmaspheric hiss. With an outer boundary condition constrained by in situ electron flux observations, we focus on the impacts of magnetopause shadowing and outward radial diffusion in the heart of the radiation belt. Third invariant conserving solutions are combined to simulate the L shell and time dependence of the differential flux at a fixed energy. ...

Ozeke, Louis; Mann, Ian; Turner, Drew; Murphy, Kyle; Degeling, Alex; Rae, Jonathan; Milling, David;

YEAR: 2014     DOI: 10.1002/2014GL060787

magnetopause shadowing; Radiation belt; ULF wave radial diffusion

Modeling Gradual Diffusion Changes in Radiation Belt Electron Phase Space Density for the March 2013 Van Allen Probes Case Study

March 2013 provided the first equinoctial period when all of the instruments on the Van Allen Probes spacecraft were fully operational. This interval was characterized by disturbances of outer zone electrons with two timescales of variation, diffusive and rapid dropout and restoration [Baker et al., 2014]. A radial diffusion model was applied to the month-long interval to confirm that electron phase space density is well described by radial diffusion for the whole month at low first invariant <=400 MeV/G, but peaks in phase ...

Li, Zhao; Hudson, Mary; Jaynes, Allison; Boyd, Alexander; Malaspina, David; Thaller, Scott; Wygant, John; Henderson, Michael;

YEAR: 2014     DOI: 10.1002/2014JA020359

March 2013; radial diffusion; Van Allen Probes

A Parametric Approach to NASA Mission Operations Costing

Quantifying the cost of mission operations can be problematic. Currently few tools exist to estimate these costs and fewer that utilize a parametric approach. This paper begins the process of developing a parametric model for estimating mission operation costs. We hypothesize that the costs of mission operations are determined by the duration and type of operation activity. For the purposes of this paper operation activities fall into the following four categories: hibernated cruise, standard cruise, flyby, and high intensit ...

Powers, Nicole;

YEAR: 2014     DOI: 10.2514/MSPACE1410.2514/6.2014-4398

Mission Control Cost

Simulation of high-energy radiation belt electron fluxes using NARMAX-VERB coupled codes

This study presents a fusion of data-driven and physics-driven methodologies of energetic electron flux forecasting in the outer radiation belt. Data-driven NARMAX (Nonlinear AutoRegressive Moving Averages with eXogenous inputs) model predictions for geosynchronous orbit fluxes have been used as an outer boundary condition to drive the physics-based Versatile Electron Radiation Belt (VERB) code, to simulate energetic electron fluxes in the outer radiation belt environment. The coupled system has been tested for three extende ...

Pakhotin, I.; . Y. Drozdov, A; . Y. Shprits, Y; Boynton, R.; Subbotin, D.; Balikhin, M.;

YEAR: 2014     DOI: 10.1002/2014JA020238

Radiation belts; Space weather

Statistical analysis of ground-based chorus observations during geomagnetic storms

Chorus observations from two ground-based, Antarctic receiving stations are analyzed for a set of geomagnetic storms from 2000 to 2010. Superposed epoch analysis is performed together with statistical hypothesis testing to determine whether the observed quantities (geomagnetic indices, outer belt energetic electron fluxes, and chorus properties) are statistically significantly different as functions of storm phase, storm size, and storm type. Waves generated in the outer dayside magnetosphere and observed on the ground at So ...

Spasojevic, M.;

YEAR: 2014     DOI: 10.1002/jgra.v119.1010.1002/2014JA019975

chorus waves; Geomagnetic storms; outer belt electrons

Survey analysis of chorus intensity at Saturn

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 ...

Menietti, J.; Averkamp, T.; Groene, J.; Horne, R.; . Y. Shprits, Y; Woodfield, E.; Hospodarsky, G.; Gurnett, D.;

YEAR: 2014     DOI: 10.1002/jgra.v119.1010.1002/2014JA020523

Space physics

THEMIS measurements of quasi-static electric fields in the inner magnetosphere

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 mode ...

Califf, S.; Li, X.; Blum, L.; Jaynes, A.; Schiller, Q.; Zhao, H.; Malaspina, D.; Hartinger, M.; Wolf, R.; Rowland, D.; Wygant, J.; Bonnell, J.;

YEAR: 2014     DOI: 10.1002/2014JA020360

convection; double probe; electric field; inner magnetosphere

On the threshold energization of radiation belt electrons by double layers

Using a Hamiltonian approach, we quantify the energization threshold of electrons interacting with radiation belts\textquoteright 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 a ...

Osmane, A.; Pulkkinen, T.;

YEAR: 2014     DOI: 10.1002/2014JA020236

Radiation belts; wave-particle interactions

The Comprehensive Inner Magnetosphere-Ionosphere Model

Simulation studies of the Earth\textquoterights 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 densit ...

Fok, M.-C.; . Y. Buzulukova, N; Chen, S.-H.; Glocer, A.; Nagai, T.; Valek, P.; Perez, J.;

YEAR: 2014     DOI: 10.1002/jgra.v119.910.1002/2014JA020239

inner magnetosphere; magnetosphere-ionosphere coupling; ring current; Radiation belts; Van Allen Probes

The effects of magnetic fields on photoelectron-mediated spacecraft potential fluctuations

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 ph ...

Wang, X.; Malaspina, D.; Hsu, H.-W.; Ergun, R.; M., Hor\;

YEAR: 2014     DOI: 10.1002/jgra.v119.910.1002/2014JA019923

chorus waves; magnetic fields; photoelectrons; spacecraft potential fluctuations; Van Allen Probes

Ground-based ELF/VLF chorus observations at subauroral latitudes-VLF-CHAIN Campaign

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\textendash25 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 withi ...

Shiokawa, Kazuo; Yokoyama, Yu; Ieda, Akimasa; Miyoshi, Yoshizumi; Nomura, Reiko; Lee, Sungeun; Sunagawa, Naoki; Miyashita, Yukinaga; Ozaki, Mitsunori; Ishizaka, Kazumasa; Yagitani, Satoshi; Kataoka, Ryuho; Tsuchiya, Fuminori; Schofield, Ian; Connors, Martin;

YEAR: 2014     DOI: 10.1002/jgra.v119.910.1002/2014JA020161

Chorus; ELF/VLF; Radiation belts; subauroral latitudes; wave-particle interactions

Magnetospheric Multiscale Science Mission Profile and Operations

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 occu ...

Fuselier, S.; Lewis, W.; Schiff, C.; Ergun, R.; Burch, J.; Petrinec, S.; Trattner, K.;

YEAR: 2014     DOI: 10.1007/s11214-014-0087-x

Magnetic reconnection; Magnetospheric multiscale; Space mission design; Spacecraft orbits

Model of electromagnetic ion cyclotron waves in the inner magnetosphere

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 stud ...

Gamayunov, K.; Engebretson, M.; Zhang, M.; Rassoul, H.;

YEAR: 2014     DOI: 10.1002/jgra.v119.910.1002/2014JA020032

electromagnetic ion cyclotron waves; outer radiation belt; ring current

Near real-time ionospheric monitoring over Europe at the Royal Observatory of Belgium using GNSS data

Various scientific applications and services increasingly demand real-time information on the effects of space weather on Earth\textquoterights 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 es ...

Bergeot, Nicolas; Chevalier, Jean-Marie; Bruyninx, Carine; Pottiaux, Eric; Aerts, Wim; Baire, Quentin; Legrand, Juliette; Defraigne, Pascale; Huang, Wei;

YEAR: 2014     DOI: 10.1051/swsc/2014028


New Twists in Earth\textquoterights Radiation Belts

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 ca ...

Baker, Daniel;

YEAR: 2014     DOI: 10.1511/2014.110.374

Van Allen Probes

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