Found 1014 entries in the Bibliography.

Showing entries from 451 through 500


In situ statistical observations of Pc1 pearl pulsations and unstructured EMIC waves by the Van Allen Probes

We present here the first in situ statistical survey of structured Pc1 pearl pulsations compared with unstructured electromagnetic ion cyclotron (EMIC) waves observed by the Van Allen Probes spacecraft. This data set was compiled from observations spanning 8 September 2012 through 31 August 2015 and comprises over 1630 h of total EMIC wave activity, of which 291 h exhibited pearl structure. Additionally, we have identified 29 wave events demonstrating periodically oscillating wave packets, mostly about the magnetic equator, ...

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

YEAR: 2016     DOI: 10.1002/2016JA023160

EMIC waves; Pc1 pearl pulsations; Van Allen Probes

Investigating the source of near-relativistic and relativistic electrons in Earth\textquoterights inner radiation belt

Using observations from NASA\textquoterights Van Allen Probes, we study the role of sudden particle enhancements at low L-shells (SPELLS) as a source of inner radiation belt electrons. SPELLS events are characterized by electron intensity enhancements of approximately an order of magnitude or more in less than one day at L < 3. During quiet and average geomagnetic conditions, the phase space density radial distributions for fixed first and second adiabatic invariants are peaked at 2 < L < 3 for electrons ranging in energy fr ...

Turner, D.; O\textquoterightBrien, T.; Fennell, J.; Claudepierre, S.; Blake, J.; Jaynes, A.; Baker, D.; Kanekal, S.; Gkioulidou, M.; Henderson, M.; Reeves, G.;

YEAR: 2016     DOI: 10.1002/2016JA023600

2720 Energetic Particles; trapped; 2730 Magnetosphere: inner; 2774 Radiation belts; 7807 Charged particle motion and acceleration; 7984 Space radiation environment; energetic particle injections; inner magnetosphere; Radiation belts; relativistic electrons; Van Allen Probes

Prompt injections of highly relativistic electrons induced by interplanetary shocks: A statistical study of Van Allen Probes observations

We conduct a statistical study on the sudden response of outer radiation belt electrons due to interplanetary (IP) shocks during the Van Allen Probes era, i.e., 2012 to 2015. Data from the Relativistic Electron-Proton Telescope instrument on board Van Allen Probes are used to investigate the highly relativistic electron response (E > 1.8 MeV) within the first few minutes after shock impact. We investigate the relationship of IP shock parameters, such as Mach number, with the highly relativistic electron response, including s ...

Schiller, Q.; Kanekal, S.; Jian, L.; Li, X.; Jones, A.; Baker, D.; Jaynes, A.; Spence, H.;

YEAR: 2016     DOI: 10.1002/2016GL071628

electrons; IP shocks; Radiation belts; Van Allen Probes

Statistical distribution of EMIC wave spectra: Observations from Van Allen Probes

It has been known that electromagnetic ion cyclotron (EMIC) waves can precipitate ultrarelativistic electrons through cyclotron resonant scattering. However, the overall effectiveness of this mechanism has yet to be quantified, because it is difficult to obtain the global distribution of EMIC waves that usually exhibit limited spatial presence. We construct a statistical distribution of EMIC wave frequency spectra and their intensities based on Van Allen Probes measurements from September 2012 to December 2015. Our results s ...

Zhang, X.-J.; Li, W.; Thorne, R.; Angelopoulos, V.; Bortnik, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.;

YEAR: 2016     DOI: 10.1002/2016GL071158

EMIC waves; magnetic storm; outer radiation belt; relativistic electron loss; Van Allen Probes; Wave-particle interaction

Transitional behavior of different energy protons based on Van Allen Probes observations

Understanding the dynamical behavior of ~1 eV to 50 keV ions and identifying the energies at which the morphologies transit are important in that they involve the relative intensities and distributions of the large-scale electric and magnetic fields, the outflow and recombination rates. However, there have been only few direct observational investigations of the transition in drift behaviors of different energy ions before the Van Allen Probes era. Here, we statistically analyze ~1 eV to 50 keV Hydrogen (H+) differential flu ...

Yue, Chao; Bortnik, Jacob; Chen, Lunjin; Ma, Qianli; Thorne, Richard; Reeves, Geoffrey; Spence, Harlan;

YEAR: 2016     DOI: 10.1002/2016GL071324

Transition in drift behavior; UBK method; Van Allen Probes

Typical values of the electric drift E \texttimes B / B 2 in the inner radiation belt and slot region as determined from Van Allen Probe measurements

The electric drift E \texttimes B/B2 plays a fundamental role for the description of plasma flow and particle acceleration. Yet it is not well-known in the inner belt and slot region because of a lack of reliable in situ measurements. In this article, we present an analysis of the electric drifts measured below L ~ 3 by both Van Allen Probes A and B from September 2012 to December 2014. The objective is to determine the typical components of the equatorial electric drift in both radial and azimuthal directions. The dependenc ...

Lejosne, ène; Mozer, F.;

YEAR: 2016     DOI: 10.1002/2016JA023613

electric drift; electric field; Inner radiation belt; plasmasphere; subcorotation; Van Allen Probes

Van Allen Probes observation of a 360\textdegree phase shift in the flux modulation of injected electrons by ULF waves

We present Van Allen Probe observation of drift-resonance interaction between energetic electrons and ultra-low frequency (ULF) waves on October 29, 2013. Oscillations in electron flux were observed at the period of \~450s, which is also the dominant period of the observed ULF magnetic pulsations. The phase shift of the electron fluxes (\~50 to 150 keV) across the estimated resonant energy (\~104 keV) is \~360\textdegree. This phase relationship is different from the characteristic 180\textdegree phase shift as expected from ...

Chen, X.-R.; Zong, Q.-G.; Zhou, X.-Z.; Blake, Bernard; Wygant, John; Kletzing, Craig;

YEAR: 2016     DOI: 10.1002/2016GL071252

drift-resonance; injection; PSD gradient; ULF waves; Van Allen Probes

Van Allen Probes Observations of Prompt MeV Radiation Belt Electron Acceleration in Non-Linear Interactions with VLF Chorus

Prompt recovery of MeV electron populations in the post-storm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly non-linear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant non-adiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by ...

Foster, J.; Erickson, P.; Omura, Y.; Baker, D.; Kletzing, C.; Claudepierre, S.;

YEAR: 2016     DOI: 10.1002/2016JA023429

nonlinear acceleration; Radiation belt; Van Allen Probes; VLF chorus; wave particle interactions

Characteristic energy range of electron scattering due to plasmaspheric hiss

We investigate the characteristic energy range of electron flux decay due to the interaction with plasmaspheric hiss in the Earth\textquoterights inner magnetosphere. The Van Allen Probes have measured the energetic electron flux decay profiles in the Earth\textquoterights outer radiation belt during a quiet period following the geomagnetic storm that occurred on 7 November 2015. The observed energy of significant electron decay increases with decreasing L shell and is well correlated with the energy band corresponding to th ...

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

YEAR: 2016     DOI: 10.1002/2016JA023311

electron flux decay; pitch angle scattering; Plasmaspheric Hiss; Van Allen Probes; Van Allen Probes observation

Comparison of Van Allen Probes radiation belt proton data with test particle simulation for the 17 March 2015 storm

The loss of protons in the outer part of the inner radiation belt (L = 2 to 3) during the 17 March 2015 geomagnetic storm was investigated using test particle simulations that follow full Lorentz trajectories with both magnetic and electric fields calculated from an empirical model. The simulation results presented here are compared with proton pitch angle measurements from the Van Allen Probe satellites Relativistic Electron Proton Telescope (REPT) instrument before and after the coronal mass ejection-shock-driven storm of ...

Engel, M.; Kress, B.; Hudson, M.; Selesnick, R.;

YEAR: 2016     DOI: 10.1002/2016JA023333

field line curvature scattering; inductive electric field; proton loss; Radiation belt; Van Allen Probes

Drift paths of ions composing multiple-nose spectral structures near the inner edge of the plasma sheet

We present a case study of the H+, He+, and O+ multiple-nose structures observed by the Helium, Oxygen, Proton, and Electron instrument on board Van Allen Probe A over one complete orbit on 28 September 2013. Nose structures are observed near the inner edge of the plasma sheet and constitute the signatures of ion drift in the highly dynamic environment of the inner magnetosphere. We find that the multiple noses are intrinsically associated with variations in the solar wind. Backward ion drift path tracings show new details o ...

Ferradas, C.; Zhang, J.-C.; Spence, H.; Kistler, L.; Larsen, B.; Reeves, G.; Skoug, R.; Funsten, H.;

YEAR: 2016     DOI: 10.1002/2016GL071359

drift path; ion injection; ion nose structure; numerical modeling; Van Allen Probes; Weimer electric field model

Ion nose spectral structures observed by the Van Allen Probes

We present a statistical study of nose-like structures observed in energetic hydrogen, helium, and oxygen ions near the inner edge of the plasma sheet. Nose structures are spectral features named after the characteristic shapes of energy bands or gaps in the energy-time spectrograms of in situ measured ion fluxes. Using 22 months of observations from the Helium Oxygen Proton Electron (HOPE) instrument onboard Van Allen Probe A, we determine the number of noses observed, and the minimum L-shell reached and energy of each nose ...

Ferradas, C.; Zhang, J.-C.; Spence, H.; Kistler, L.; Larsen, B.; Reeves, G.; Skoug, R.; Funsten, H.;

YEAR: 2016     DOI: 10.1002/2016JA022942

inner magnetosphere; ion injection; Ion structure; plasma sheet; ring current; Van Allen Probes

Ring Current Pressure Estimation with RAM-SCB using Data Assimilation and Van Allen Probe Flux Data

Capturing and subsequently modeling the influence of tail plasma injections on the inner magnetosphere is important for understanding the formation and evolution of the ring current. In this study, the ring current distribution is estimated with the Ring Current-Atmosphere Interactions Model with Self-Consistent Magnetic field (RAM-SCB) using, for the first time, data assimilation techniques and particle flux data from the Van Allen Probes. The state of the ring current within the RAM-SCB model is corrected via an ensemble b ...

Godinez, Humberto; Yu, Yiqun; Lawrence, Eric; Henderson, Michael; Larsen, Brian; Jordanova, Vania;

YEAR: 2016     DOI: 10.1002/2016GL071646

data assimilation; ring current; Van Allen Probes

Van Allen Probes observations of cross-scale coupling between electromagnetic ion cyclotron waves and higher-frequency wave modes

We present observations of higher-frequency (~50\textendash2500 Hz, ~0.1\textendash0.7 fce) wave modes modulated at the frequency of colocated lower frequency (0.5\textendash2 Hz, on the order of fci) waves. These observations come from the Van Allen Probes Electric Field and Waves instrument\textquoterights burst mode data and represent the first observations of coupling between waves in these frequency ranges. The higher-frequency wave modes, typically whistler mode hiss and chorus or magnetosonic waves, last for a few to ...

Colpitts, C.; Cattell, C.; Engebretson, M.; Broughton, M.; Tian, S.; Wygant, J.; Breneman, A.; Thaller, S.;

YEAR: 2016     DOI: 10.1002/2016GL071566

EMIC; Modulation; precipitation; Radiation belt; Van Allen Probes; wave; whistler

Void structure of O + ions in the inner magnetosphere observed by the Van Allen Probes

The Van Allen Probes Helium Oxygen Proton Electron instrument observed a new type of enhancement of O+ ions in the inner magnetosphere during substorms. As the satellite moved outward in the premidnight sector, the flux of the O+ ions with energy ~10 keV appeared first in the energy-time spectrograms. Then, the enhancement of the flux spread toward high and low energies. The enhanced flux of the O+ ions with the highest energy remained, whereas the flux of the ions with lower energy vanished near apogee, forming what we call ...

Nakayama, Y.; Ebihara, Y.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L.; Tanaka, T.;

YEAR: 2016     DOI: 10.1002/2016JA023013

injections; nonadiabatic acceleration; substorms; Van Allen Probes

EMIC waves and associated relativistic electron precipitation on 25-26 January 2013

Using measurements from the Van Allen Probes and the Balloon Array for RBSP Relativistic Electron Losses (BARREL), we perform a case study of electromagnetic ion cyclotron (EMIC) waves and associated relativistic electron precipitation (REP) observed on 25\textendash26 January 2013. Among all the EMIC wave and REP events from the two missions, the pair of the events is the closest both in space and time. The Van Allen Probe-B detected significant EMIC waves at L = 2.1\textendash3.9 and magnetic local time (MLT) = 21.0\texten ...

Zhang, Jichun; Halford, Alexa; Saikin, Anthony; Huang, Chia-Lin; Spence, Harlan; Larsen, Brian; Reeves, Geoffrey; Millan, Robyn; Smith, Charles; Torbert, Roy; Kurth, William; Kletzing, Craig; Blake, Bernard; Fennel, Joseph; Baker, Daniel;

YEAR: 2016     DOI: 10.1002/2016JA022918

BARREL; EMIC waves; FFT; Geomagnetic storm; relativistic electron precipitation (REP); Van Allen Probes

Mesospheric ozone destruction by high-energy electron precipitation associated with pulsating aurora

Energetic particle precipitation into the upper atmosphere creates excess amounts of odd nitrogen and odd hydrogen. These destroy mesospheric and upper stratospheric ozone in catalytic reaction chains, either in situ at the altitude of the energy deposition or indirectly due to transport to other altitudes and latitudes. Recent statistical analysis of satellite data on mesospheric ozone reveals that the variations during energetic electron precipitation from Earth\textquoterights radiation belts can be tens of percent. Here ...

Turunen, Esa; Kero, Antti; Verronen, Pekka; Miyoshi, Yoshizumi; Oyama, Shin-Ichiro; Saito, Shinji;

YEAR: 2016     DOI: 10.1002/2016JD025015

EISCAT; electron precipitation; ion chemistry; mesosphere; ozone; pulsating aurora; Van Allen Probes

A new method to study the time correlation between Van Allen Belt electrons and earthquakes

A new method to study a possible temporal correlation between hundreds of keV Van Allen Belt electrons and strong earthquakes is proposed. It consists in measuring the electrons pitch angle distribution (PAD), searching for PAD disturbances, and studying the time correlation between these PAD disturbances and strong earthquakes, occurring within a defined time window. The method was applied to measurements of energetic electrons, which were performed with the Energetic Particle, Composition, and Thermal Plasma (ECT)-MagEIS d ...

Tao, Dan; Battiston, Roberto; Vitale, Vincenzo; Burger, William; Lazzizzera, Ignazio; Cao, Jinbin; Shen, Xuhui;

YEAR: 2016     DOI: 10.1080/01431161.2016.1239284

Van Allen Probes

The complex nature of storm-time ion dynamics: Transport and local acceleration

Data from the Van Allen Probes Helium, Oxygen, Proton, Electron (HOPE) spectrometers reveal hitherto unresolved spatial structure and dynamics in ion populations. Complex regions of O+ dominance, at energies from a few eV to >10 keV, are observed throughout the magnetosphere. Isolated regions on the dayside that are rich in energetic O+ might easily be interpreted as strong energization of ionospheric plasma. We demonstrate, however, that both the energy spectrum and the limited MLT extent of these features can be explained ...

Denton, M.; Reeves, G.; Thomsen, M.; Henderson, M.; Friedel, R.; Larsen, B.; Skoug, R.; Funsten, H.; Spence, H.; Kletzing, C.;

YEAR: 2016     DOI: 10.1002/2016GL070878

plasmasheet; Van Allen Probes

Current energetic particle sensors

Several energetic particle sensors designed to make measurements in the current decade are described and their technology and capabilities discussed and demonstrated. Most of these instruments are already on orbit or approaching launch. These include the Magnetic Electron Ion Spectrometers (MagEIS) and the Relativistic Electron Proton Telescope (REPT) that are flying on the Van Allen Probes, the Fly\textquoterights Eye Electron Proton Spectrometers (FEEPS) flying on the Magnetospheric Multiscale (MMS) mission, and Dosimeters ...

Fennell, J.; Blake, J.; Claudepierre, S.; Mazur, J.; Kanekal, S.; O\textquoterightBrien, P.; Baker, D.; Crain, W.; Mabry, D.; Clemmons, J.;

YEAR: 2016     DOI: 10.1002/2016JA022588

energetic particles; sensors; Van Allen Probes

Hiss or Equatorial Noise? Ambiguities in Analyzing Suprathermal Ion Plasma Wave Resonance

Previous studies have shown that low energy ion heating occurs in the magnetosphere due to strong equatorial noise emission. Observations from the Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument recently determined there was a depletion in the 1-10 eV ion population in the post-midnight sector of Earth during quiet times at L < 3. The diurnal variation of equatorially mirroring 1-10 eV H+ ions between 2 < L < 3 is connected with similar diurnal variation in the electric field component of plasma waves rangin ...

Sarno-Smith, Lois; Liemohn, Michael; Skoug, Ruth; ik, Ondrej; Morley, Steven; Breneman, Aaron; Larsen, Brian; Reeves, Geoff; Wygant, John; Hospodarsky, George; Kletzing, Craig; Moldwin, Mark; Katus, Roxanne; Zou, Shasha;

YEAR: 2016     DOI: 10.1002/2016JA022975

equatorial noise; Low Energy Ions; plasma waves; plasmasphere; Plasmaspheric Hiss; Van Allen Probes

Modulation of chorus intensity by ULF waves deep in the inner magnetosphere

Previous studies have shown that chorus wave intensity can be modulated by Pc4-Pc5 compressional ULF waves. In this study, we present Van Allen Probes observation of ULF wave modulating chorus wave intensity, which occurred deep in the magnetosphere. The ULF wave shows fundamental poloidal mode signature and mirror mode compressional nature. The observed ULF wave can modulate not only the chorus wave intensity but also the distribution of both protons and electrons. Linear growth rate analysis shows consistence with observed ...

Xia, Zhiyang; Chen, Lunjin; Dai, Lei; Claudepierre, Seth; Chan, Anthony; Soto-Chavez, A.; Reeves, G.;

YEAR: 2016     DOI: 10.1002/2016GL070280

chorus modulation; inner magnetosphere; ULF wave; Van Allen Probes; whistler wave

A new ionospheric electron precipitation module coupled with RAM-SCB within the geospace general circulation model

Electron precipitation down to the atmosphere due to wave-particle scattering in the magnetosphere contributes significantly to the auroral ionospheric conductivity. In order to obtain the auroral conductivity in global MHD models that are incapable of capturing kinetic physics in the magnetosphere, MHD parameters are often used to estimate electron precipitation flux for the conductivity calculation. Such an MHD approach, however, lacks self-consistency in representing the magnetosphere-ionosphere coupling processes. In thi ...

Yu, Yiqun; Jordanova, Vania; Ridley, Aaron; Albert, Jay; Horne, Richard; Jeffery, Christopher;

YEAR: 2016     DOI: 10.1002/2016JA022585

Diffusion Coefficient; electron lifetime; electron precipitation; ionospheric conductivity; MI coupling; Van Allen Probes; wave-particle interactions

Observational evidence of the nonlinear wave growth theory of plasmaspheric hiss

We test the recently developed nonlinear wave growth theory of plasmaspheric hiss against discrete rising tone elements of hiss emissions observed by the Van Allen Probes. From the phase variation of the waveforms processed by bandpass filters, we calculate the instantaneous frequencies and wave amplitudes. We obtain the theoretical relation between the wave amplitude and frequency sweep rates at the observation point by applying the convective growth rates and dispersion factors to the known relation at the equator. By plot ...

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

YEAR: 2016     DOI: 10.1002/2016GL070333

magnetospheric dynamics; nonlinear wave growth theory; plasma wave; Plasmaspheric Hiss; Van Allen Probes; whistler-mode chorus

The permeability of the magnetopause to a multispecies substorm injection of energetic particles

Leakage of ions from the magnetosphere into the magnetosheath remains an important topic in understanding the plasma physics of Earth\textquoterights magnetopause and the interaction of the solar wind with the magnetosphere. Here using sophisticated instrumentation from two spacecraft (Radiation Belt Storm Probes Ion Composition Experiment on the Van Allen Probes and Energetic Ion Spectrometer on the Magnetospheric Multiscale) spaced uniquely near and outside the dayside magnetopause, we are able to determine the escape mech ...

Westlake, J.; Cohen, I.; Mauk, B.; Anderson, B.; Mitchell, D.; Gkioulidou, M.; Walsh, B.; Lanzerotti, L.; Strangeway, R.; Russell, C.;

YEAR: 2016     DOI: 10.1002/2016GL070189

energetic particles; magnetopause; magnetosheath; MMSEPD; Van Allen Probes

Physical mechanism causing rapid changes in ultrarelativistic electron pitch angle distributions right after a shock arrival: Evaluation of an electron dropout event

Three mechanisms have been proposed to explain relativistic electron flux depletions (dropouts) in the Earth\textquoterights outer radiation belt during storm times: adiabatic expansion of electron drift shells due to a decrease in magnetic field strength, magnetopause shadowing and subsequent outward radial diffusion, and precipitation into the atmosphere (driven by EMIC wave scattering). Which mechanism predominates in causing electron dropouts commonly observed in the outer radiation belt is still debatable. In the presen ...

Zhang, X.-J.; Li, W.; Thorne, R.; Angelopoulos, V.; Ma, Q.; Li, J.; Bortnik, J.; Nishimura, Y.; Chen, L.; Baker, D.; Reeves, G.; Spence, H.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Blake, J.; Fennell, J.;

YEAR: 2016     DOI: 10.1002/2016JA022517

Drift shell splitting; dropouts; magnetic storm; magnetopause shadowing; outer radiation belt; relativistic electron loss; Van Allen Probes

RAM-SCB simulations of electron transport and plasma wave scattering during the October 2012 \textquotedblleftdouble-dip\textquotedblright storm

Mechanisms for electron injection, trapping, and loss in the near-Earth space environment are investigated during the October 2012 \textquotedblleftdouble-dip\textquotedblright storm using our ring current-atmosphere interactions model with self-consistent magnetic field (RAM-SCB). Pitch angle and energy scattering are included for the first time in RAM-SCB using L and magnetic local time (MLT)-dependent event-specific chorus wave models inferred from NOAA Polar-orbiting Operational Environmental Satellites (POES) and Van Al ...

Jordanova, V.; Tu, W.; Chen, Y.; Morley, S.; Panaitescu, A.-D.; Reeves, G.; Kletzing, C.;

YEAR: 2016     DOI: 10.1002/2016JA022470

Geomagnetic storms; inner magnetosphere; Van Allen Probes

RBSPICE measurement of ion loss during the 2015 March storm: Adiabatic response to the geomagnetic field change

A strongly energy-dependent ring current ion loss was measured by the RBSPICE instrument on the Van Allen Probes A spacecraft in the local evening sector during the 17 March 2015 geomagnetic storm. The ion loss is found to be energy dependent where only ions with energies measured above \~ 150 keV have a significant drop in intensity. At these energies the ion dynamics are principally controlled by variations of the geomagnetic field which, during magnetic storms, exhibits large scale variations on timescales from minutes ...

Soto-Chavez, A.; Lanzerotti, L.; Gerrard, A.; Kim, H.; Bortnik, J.; Manweiler, J.;

YEAR: 2016     DOI: 10.1002/2016JA022512

inner magnetosphere; Magnetic Storms; Ring current ion.; Van Allen Probes

Unraveling the excitation mechanisms of highly oblique lower band chorus waves

Excitation mechanisms of highly oblique, quasi-electrostatic lower band chorus waves are investigated using Van Allen Probes observations near the equator of the Earth\textquoterights magnetosphere. Linear growth rates are evaluated based on in situ, measured electron velocity distributions and plasma conditions and compared with simultaneously observed wave frequency spectra and wave normal angles. Accordingly, two distinct excitation mechanisms of highly oblique lower band chorus have been clearly identified for the first ...

Li, W.; Mourenas, D.; Artemyev, A.; Bortnik, J.; Thorne, R.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Reeves, G.; Funsten, H.; Spence, H.;

YEAR: 2016     DOI: 10.1002/grl.v43.1710.1002/2016GL070386

beam instability; lower band chorus; oblique chorus excitation; temperature anisotropy; Van Allen Probes

Van Allen Probes Observations of Electromagnetic Ion Cyclotron Waves Triggered by Enhanced Solar Wind Dynamic Pressure

Magnetospheric compression due to impact of enhanced solar wind dynamic pressure Pdyn has long been considered as one of the generation mechanisms of electromagnetic ion cyclotron (EMIC) waves. With the Van Allen Probe-A observations, we identify three EMIC wave events that are triggered by Pdyn enhancements under prolonged northward IMF quiet time preconditions. They are in contrast to one another in a few aspects. Event 1 occurs in the middle of continuously increasing Pdyn while Van Allen Probe-A is located outside the pl ...

Cho, J.-H.; Lee, D.-Y.; Noh, S.-J.; Shin, D.-K.; Hwang, J.; Kim, K.-C.; Lee, J.; Choi, C.; Thaller, S.; Skoug, R.;

YEAR: 2016     DOI: 10.1002/2016JA022841

Dynamic pressure; EMIC waves; Van Allen Probes

Van Allen Probes observations of oxygen cyclotron harmonic waves in the inner magnetosphere

Waves with frequencies in the vicinity of the oxygen cyclotron frequency and its harmonics have been regularly observed on the Van Allen Probes satellites during geomagnetic storms. We focus on properties of these waves and present events from the main phase of two storms on 1 November 2012 and 17 March 2013 and associated dropouts of a few MeV electron fluxes. They are electromagnetic, in the frequency range ~0.5 to several Hz, and amplitude ~0.1 to a few nT in magnetic and ~0.1 to a few mV/m in electric field, with both th ...

Usanova, M.; Malaspina, D.; Jaynes, A.; Bruder, R.; Mann, I.; Wygant, J.; Ergun, R.;

YEAR: 2016     DOI: 10.1002/grl.v43.1710.1002/2016GL070233

cyclotron harmonic waves; energetic particle loss; Geomagnetic storms; inner magnetosphere; oxygen; Van Allen Probes

Wave-driven gradual loss of energetic electrons in the slot region

Resonant pitch angle scattering by plasmaspheric hiss has long been considered to be responsible for the energetic electron loss in the slot region, but the detailed quantitative comparison between theory and observations is still lacking. Here we focus on the loss of 100\textendash600 keV electrons at L = 3 during the recovery phase of a geomagnetic storm on 28 June 2013. Van Allen Probes data showed the concurrence of intense (with power up to 10-4 nT2/Hz) plasmaspheric hiss waves and significant (up to 1 order) loss of en ...

He, Zhaoguo; Yan, Qi; Chu, Yuchuan; Cao, Yong;

YEAR: 2016     DOI: 10.1002/2016JA023087

electron loss; energetic electron; Plasmaspheric Hiss; Slot region; Van Allen Probes; Wave-particle interaction

Conjugate observations of quasiperiodic emissions by the Cluster, Van Allen Probes, and THEMIS spacecraft

We present results of a detailed analysis of two electromagnetic wave events observed in the inner magnetosphere at frequencies of a few kilohertz, which exhibit a quasiperiodic (QP) time modulation of the wave intensity. The events were observed by the Cluster and Van Allen Probes spacecraft and in one event also by the THEMIS E spacecraft. The spacecraft were significantly separated in magnetic local time, demonstrating a huge azimuthal extent of the events. Geomagnetic conditions at the times of the observations were very ...

emec, F.; Hospodarsky, G.; Pickett, J.; ik, O.; Kurth, W.; Kletzing, C.;

YEAR: 2016     DOI: 10.1002/2016JA022774

QP emissions; quasiperiodic emissions; Van Allen Probes

Control of the innermost electron radiation belt by large-scale electric fields

Electron measurements from the Magnetic Electron Ion Spectrometer instruments on Van Allen Probes, for kinetic energies \~100 to 400 keV, show characteristic dynamical features of the innermost ( inline image) radiation belt: rapid injections, slow decay, and structured energy spectra. There are also periods of steady or slowly increasing intensity and of fast decay following injections. Local time asymmetry, with higher intensity near dawn, is interpreted as evidence for drift shell distortion by a convection electric field ...

Selesnick, R.; Su, Y.-J.; Blake, J.;

YEAR: 2016     DOI: 10.1002/2016JA022973

electric field; electrons; Inner radiation belt; Van Allen Probes

The distribution of plasmaspheric hiss wave power with respect to plasmapause location

In this work, Van Allen Probes data are used to derive terrestrial plasmaspheric hiss wave power distributions organized by (1) distance away from the plasmapause and (2) plasmapause distance from Earth. This approach is in contrast to the traditional organization of hiss wave power by L parameter and geomagnetic activity. Plasmapause-sorting reveals previously unreported and highly repeatable features of the hiss wave power distribution, including a regular spatial distribution of hiss power with respect to the plasmapause, ...

Malaspina, David; Jaynes, Allison; e, Cory; Bortnik, Jacob; Thaller, Scott; Ergun, Robert; Kletzing, Craig; Wygant, John;

YEAR: 2016     DOI: 10.1002/2016GL069982

hiss; plasma waves; plasmasphere; Radiation belts; Van Allen Probes

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

Energy limits of electron acceleration in the plasma sheet during substorms: A case study with the Magnetospheric Multiscale (MMS) mission

We present multipoint observations of earthward moving dipolarization fronts and energetic particle injections from NASA\textquoterights Magnetospheric Multiscale mission with a focus on electron acceleration. From a case study during a substorm on 02 August 2015, we find that electrons are only accelerated over a finite energy range, from a lower energy threshold at ~7\textendash9 keV up to an upper energy cutoff in the hundreds of keV range. At energies lower than the threshold energy, electron fluxes decrease, potentially ...

Turner, D.; Fennell, J.; Blake, J.; Clemmons, J.; Mauk, B.; Cohen, I.; Jaynes, A.; Craft, J.; Wilder, F.; Baker, D.; Reeves, G.; Gershman, D.; Avanov, L.; Dorelli, J.; Giles, B.; Pollock, C.; Schmid, D.; Nakamura, R.; Strangeway, R.; Russell, C.; Artemyev, A.; Runov, A.; Angelopoulos, V.; Spence, H.; Torbert, R.; Burch, J.;

YEAR: 2016     DOI: 10.1002/2016GL069691

energetic particle injections; magnetotail; Particle acceleration; plasma sheet; reconnection; substorm; Van Allen Probes

Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes

To understand the role of electromagnetic ion cyclotron (EMIC) waves in determining the temporal features of pulsating proton aurora (PPA) via wave-particle interactions at subauroral latitudes, high-time-resolution (1/8 s) images of proton-induced N2+ emissions were recorded using a new electron multiplying charge-coupled device camera, along with related Pc1 pulsations on the ground. The observed Pc1 pulsations consisted of successive rising-tone elements with a spacing for each element of 100 s and subpacket structures, w ...

Ozaki, M.; Shiokawa, K.; Miyoshi, Y.; Kataoka, R.; Yagitani, S.; Inoue, T.; Ebihara, Y.; Jun, C.-W; Nomura, R.; Sakaguchi, K.; Otsuka, Y.; Shoji, M.; Schofield, I.; Connors, M.; Jordanova, V.;

YEAR: 2016     DOI: 10.1002/2016GL070008

fast modulation; Pc1 geomagnetic pulsations; pulsating proton aurora; subpacket structure; Van Allen Probes; wave-particle interactions

Formation of the inner electron radiation belt by enhanced large-scale electric fields

A two-dimensional bounce-averaged test particle code was developed to examine trapped electron trajectories during geomagnetic storms with the assumption of conservation of the first and second adiabatic invariants. The March 2013 storm was selected as an example because the geomagnetic activity Kp index sharply increased from 2 + to 7- at 6:00 UT on 17 March. Electron measurements with energies between 37 and 460 keV from the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard Van Allen Probes (VAP) are used as i ...

Su, Yi-Jiun; Selesnick, Richard; Blake, J.;

YEAR: 2016     DOI: 10.1002/2016JA022881

DC electric fields; electron injections; Inner radiation belt; test particle simulation; Van Allen Probes; Van Allen Probes electron measurements

Observation of chorus waves by the Van Allen Probes: Dependence on solar wind parameters and scale size

Highly energetic electrons in the Earth\textquoterights Van Allen radiation belts can cause serious damage to spacecraft electronic systems and affect the atmospheric composition if they precipitate into the upper atmosphere. Whistler mode chorus waves have attracted significant attention in recent decades for their crucial role in the acceleration and loss of energetic electrons that ultimately change the dynamics of the radiation belts. The distribution of these waves in the inner magnetosphere is commonly presented as a f ...

Aryan, Homayon; Sibeck, David; Balikhin, Michael; Agapitov, Oleksiy; Kletzing, Craig;

YEAR: 2016     DOI: 10.1002/jgra.v121.810.1002/2016JA022775

distribution of chorus wave intensities in the inner magnetosphere; inner magnetosphere; Radiation belts; scale size of chorus wave packets; Van Allen Probes; Wave-particle interaction

Prompt acceleration of magnetospheric electrons to ultrarelativistic energies by the 17 March 2015 interplanetary shock

Trapped electrons in Earth\textquoterights outer Van Allen radiation belt are influenced profoundly by solar phenomena such as high-speed solar wind streams, coronal mass ejections (CME), and interplanetary (IP) shocks. In particular, strong IP shocks compress the magnetosphere suddenly and result in rapid energization of electrons within minutes. It is believed that the electric fields induced by the rapid change in the geomagnetic field are responsible for the energization. During the latter part of March 2015, a CME impac ...

Kanekal, S.; Baker, D.; Fennell, J.; Jones, A.; Schiller, Q.; Richardson, I.; Li, X.; Turner, D.; Califf, S.; Claudepierre, S.; Wilson, L.; Jaynes, A.; Blake, J.; Reeves, G.; Spence, H.; Kletzing, C.; Wygant, J.;

YEAR: 2016     DOI: 10.1002/2016JA022596

electron; energizaiton; IP shock; ultrarelativsti; Van Allen Probes

Propagation of ULF waves from the upstream region to the midnight sector of the inner magnetosphere

Ultralow frequency (ULF) waves generated in the ion foreshock are a well-known source of Pc3-Pc4 waves (7\textendash100 mHz) observed in the dayside magnetosphere. We use data acquired on 10 April 2013 by multiple spacecraft to demonstrate that ULF waves of upstream origin can propagate to the midnight sector of the inner magnetosphere. At 1130\textendash1730 UT on the selected day, the two Van Allen Probes spacecraft and the geostationary ETS-VIII satellite detected compressional 20 to 40 mHz magnetic field oscillations bet ...

Takahashi, Kazue; Hartinger, Michael; Malaspina, David; Smith, Charles; Koga, Kiyokazu; Singer, Howard; ühauff, Dennis; Baishev, Dmitry; Moiseev, Alexey; Yoshikawa, Akimasa;

YEAR: 2016     DOI: 10.1002/2016JA022958

midnight sector; Pc3 waves; plasmasphere; upstream waves; Van Allen Probes

The relationship between the macroscopic state of electrons and the properties of chorus waves observed by the Van Allen Probes

Plasma kinetic theory predicts that a sufficiently anisotropic electron distribution will excite whistler mode waves, which in turn relax the electron distribution in such a way as to create an upper bound on the relaxed electron anisotropy. Here using whistler mode chorus wave and plasma measurements by Van Allen Probes, we confirm that the electron distributions are well constrained by this instability to a marginally stable state in the whistler mode chorus waves generation region. Lower band chorus waves are organized by ...

Yue, Chao; An, Xin; Bortnik, Jacob; Ma, Qianli; Li, Wen; Thorne, Richard; Reeves, Geoffrey; Gkioulidou, Matina; Mitchell, Donald; Kletzing, Craig;

YEAR: 2016     DOI: 10.1002/2016GL070084

beta parallel; electron temperature anisotropy; marginally stable state; oblique waves; quasi-parallel waves; Van Allen Probes; whistler mode chorus waves

The relationship between the plasmapause and outer belt electrons

We quantify the spatial relationship between the plasmapause and outer belt electrons for a 5 day period, 15\textendash20 January 2013, by comparing locations of relativistic electron flux peaks to the plasmapause. A peak-finding algorithm is applied to 1.8\textendash7.7 MeV relativistic electron flux data. A plasmapause gradient finder is applied to wave-derived electron number densities >10 cm-3. We identify two outer belts. Outer belt 1 is a stable zone of >3 MeV electrons located 1\textendash2 RE inside the plasmapause. ...

Goldstein, J.; Baker, D.; Blake, J.; De Pascuale, S.; Funsten, H.; Jaynes, A.; Jahn, J.-M.; Kletzing, C.; Kurth, W.; Li, W.; Reeves, G.; Spence, H.;

YEAR: 2016     DOI: 10.1002/2016JA023046

Plasmapause; Plasmaspheric Hiss; Radiation belts; simulation; storm-time dropouts; Van Allen Probes

Storm time impulsive enhancements of energetic oxygen due to adiabatic acceleration of preexisting warm oxygen in the inner magnetosphere

We examine enhancements of energetic (>50 keV) oxygen ions observed by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on board the Van Allen Probes spacecraft in the inner magnetosphere (L ~ 6) at 22\textendash23 h magnetic local time (MLT) during an injection event of the 6 June 2013 storm. Simultaneous observations by two Van Allen Probes spacecraft located close together (~0.5 RE) indicate that particle injections occurred in the premidnight sector (< ~24 h MLT). We also examine the evolut ...

Keika, Kunihiro; Seki, Kanako; e, Masahito; Machida, Shinobu; Miyoshi, Yoshizumi; Lanzerotti, Louis; Mitchell, Donald; Gkioulidou, Matina; Turner, Drew; Spence, Harlan; Larsen, Brian;

YEAR: 2016     DOI: 10.1002/2016JA022384

adiabatic transport from the plasma sheet; oxygen ions of ionospheric origin; preconditions of magnetic storms; preexisting oxygen ions trapped in the inner magnetosphere; Van Allen Probes; Van Allen Probes RBSPICE observations

Direct evidence for EMIC wave scattering of relativistic electrons in space

Electromagnetic ion cyclotron (EMIC) waves have been proposed to cause efficient losses of highly relativistic (>1 MeV) electrons via gyroresonant interactions. Simultaneous observations of EMIC waves and equatorial electron pitch angle distributions, which can be used to directly quantify the EMIC wave scattering effect, are still very limited, however. In the present study, we evaluate the effect of EMIC waves on pitch angle scattering of ultrarelativistic (>1 MeV) electrons during the main phase of a geomagnetic storm, wh ...

Zhang, X.-J.; Li, W.; Ma, Q.; Thorne, R.; Angelopoulos, V.; Bortnik, J.; Chen, L.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Baker, D.; Reeves, G.; Spence, H.; Blake, J.; Fennell, J.;

YEAR: 2016     DOI: 10.1002/2016JA022521

electron precipitation; EMIC waves; equatorial pitch angle distribution; Fokker-Planck equation; relativistic electron loss; Van Allen Probes; Wave-particle interaction

Global ULF wave analysis of radial diffusion coefficients using a global MHD model for the 17 March 2015 storm

The 17\textendash18 March 2015 storm is the largest geomagnetic storm in the Van Allen Probes era to date. The Lyon-Fedder-Mobarry global MHD model has been run for this event using ARTEMIS data as solar wind input. The ULF wave power spectral density of the azimuthal electric field and compressional magnetic field is analyzed in the 0.5\textendash8.3 mHz range. The lowest three azimuthal modes account for 70\% of the total power during quiet times. However, during high activity, they are not exclusively dominant. The calcul ...

Li, Zhao; Hudson, Mary; Paral, Jan; Wiltberger, Michael; Turner, Drew;

YEAR: 2016     DOI: 10.1002/2016JA022508

March 2015; radial diffusion; radial diffusion coefficient; Radiation belt; ULF waves; Van Allen Probes

In situ evidence of the modification of the parallel propagation of EMIC waves by heated He + ions

With observations of the Van Allen Probe B, we report in situ evidence of the modification of the parallel propagating electromagnetic ion cyclotron (EMIC) waves by heated He+ ions. In the outer boundary of the plasmasphere, accompanied with the He+ ion heating, the frequency bands of H+ and He+ for EMIC waves merged into each other, leading to the disappearance of a usual stop band between the gyrofrequency of He+ ions (ΩHe+) and the H+ cutoff frequency (ωH+co) in the cold plasma. Moreover, the dispersion relation for EMI ...

Yuan, Zhigang; Yu, Xiongdong; Wang, Dedong; Huang, Shiyong; Li, Haimeng; Yu, Tao; Qiao, Zheng; Wygant, John; Funsten, Herbert;

YEAR: 2016     DOI: 10.1002/2016JA022573

EMIC waves; He+ ion heating; Ring current ions; stop band; Van Allen Probes

Inner zone and slot electron radial diffusion revisited

Using recent data from NASA\textquoterights Van Allen Probes, we estimate the quiet time radial diffusion coefficients for electrons in the inner radiation belt (L < 3) with energies from ~50 to 750 keV. The observations are consistent with dynamics dominated by pitch angle scattering and radial diffusion. We use a coordinate system in which these two modes of diffusion are separable. Then we integrate phase space density over pitch angle to obtain a \textquotedblleftbundle content\textquotedblright that is invariant to pitc ...

O\textquoterightBrien, T.; Claudepierre, S.; Guild, T.; Fennell, J.; Turner, D.; Blake, J.; Clemmons, J.; Roeder, J.;

YEAR: 2016     DOI: 10.1002/2016GL069749

Inner zone; radial diffusion; Radiation belt; Van Allen Probes

Local time variations of high-energy plasmaspheric ion pitch angle distributions

Recent observations from the Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument revealed a persistent depletion in the 1\textendash10 eV ion population in the postmidnight sector during quiet times in the 2 < L < 3 region. This study explores the source of this ion depletion by developing an algorithm to classify 26 months of pitch angle distributions measured by the HOPE instrument. We correct the HOPE low energy fluxes for spacecraft potential using measurements from the Electric Field and Waves (EFW) instrum ...

Sarno-Smith, Lois; Liemohn, Michael; Skoug, Ruth; Larsen, Brian; Moldwin, Mark; Katus, Roxanne; Wygant, John;

YEAR: 2016     DOI: 10.1002/2015JA022301

algorithm; Magnetosphere; pitch angles; plasmasphere; spacecraft potential corrections; Van Allen Probes

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