Bibliography



Found 938 entries in the Bibliography.


Showing entries from 301 through 350


2017

Roles of hot electrons in generating upper-hybrid waves in the earth\textquoterights radiation belt

Electrostatic fluctuations near upper-hybrid frequency, which are sometimes accompanied by multiple-harmonic electron cyclotron frequency bands above and below the upper-hybrid frequency, are common occurrences in the Earth\textquoterights radiation belt, as revealed through the twin Van Allen Probe spacecrafts. It is customary to use the upper-hybrid emissions for estimating the background electron density, which in turn can be used to determine the plasmapause locations, but the role of hot electrons in generating such flu ...

Hwang, J.; Shin, D.; Yoon, P.; Kurth, W.; Larsen, B.; Reeves, G.; . Y. Lee, D;

YEAR: 2017     DOI: 10.1063/1.4984249

Hot carriers; Magnetized plasmas; Radiation belts; Singing; Van Allen Probes; Whistler waves

ULF Wave Analysis and Radial Diffusion Calculation Using a Global MHD Model for the 17 March 2013 and 2015 Storms

The 17 March 2015 St. Patrick\textquoterights Day Storm is the largest geomagnetic storm to date of Solar Cycle 24, with a Dst of -223 nT. The magnetopause moved inside geosynchronous orbit under high solar wind dynamic pressure and strong southward IMF Bz causing loss, however a subsequent drop in pressure allowed for rapid rebuilding of the radiation belts. The 17 March 2013 storm also shows similar effects on outer zone electrons: first a rapid dropout due to inward motion of the magnetopause followed by rapid increase in ...

Li, Zhao; Hudson, Mary; Patel, Maulik; Wiltberger, Michael; Boyd, Alex; Turner, Drew;

YEAR: 2017     DOI: 10.1002/2016JA023846

March 2013; March 2015; radial diffusion; Radiation belt; Van Allen Probes

Unusual refilling of the slot region between the Van Allen radiation belts from November 2004 to January 2005

Using multisatellite measurements, a uniquely strong and long-lived relativistic electron slot region refilling event from November 2004 to January 2005 is investigated. This event occurred under remarkable interplanetary and magnetospheric conditions. Both empirically modeled and observationally estimated plasmapause locations demonstrate that the plasmasphere eroded significantly prior to the enhancement phase of this event. The estimated diffusion coefficients indicate that the radial diffusion due to ULF waves is insuffi ...

Yang, Xiaochao; Ni, Binbin; Yu, Jiang; Zhang, Yang; Zhang, Xiaoxin; Sun, Yueqiang;

YEAR: 2017     DOI: 10.1002/2016JA023204

Radiation belt; Relativistic electron; Slot region; Van Allen Probes

Van Allen Probes observations of whistler-mode chorus with long-lived oscillating tones

Whistler-mode chorus plays an important role in the radiation belt electron dynamics. In the frequency-time spectrogram, chorus often appears as a hiss-like band and/or a series of short-lived (up to \~1 s) discrete elements. Here we present some rarely reported chorus emissions with long-lived (up to 25 s) oscillating tones observed by the Van Allen Probes in the dayside (MLT \~9\textendash14) midlatitude (|MLAT|>15\textdegree) region. An oscillating tone can behave either regularly or irregularly and can even transform int ...

Gao, Zhonglei; Su, Zhenpeng; Chen, Lunjin; Zheng, Huinan; Wang, Yuming; Wang, Shui;

YEAR: 2017     DOI: 10.1002/2017GL073420

Chorus; falling tone; nonlinear generation; oscillating tone; rising tone; Van Allen Probes

VLF waves from ground-based transmitters observed by the Van Allen Probes: Statistical model and effects on plasmaspheric electrons

Whistler-mode Very Low Frequency (VLF) waves from powerful ground-based transmitters can resonantly scatter energetic plasmaspheric electrons and precipitate them into the atmosphere. A comprehensive 4-year statistics of Van Allen Probes measurements is carried out to assess their consequences on the dynamics of the inner radiation belt and slot region. Statistical models of the measured wave electric field power and of the inferred full wave magnetic amplitude are provided as a function of L, magnetic local time, season, an ...

Ma, Qianli; Mourenas, Didier; Li, Wen; Artemyev, Anton; Thorne, Richard;

YEAR: 2017     DOI: 10.1002/2017GL073885

Electron scattering; Statistical wave model; Van Allen Probes; Van Allen Probes observation; VLF waves

Effects of whistler mode hiss waves in March 2013

We present simulations of the loss of radiation belt electrons by resonant pitch angle diffusion caused by whistler mode hiss waves for March 2013. Pitch angle diffusion coefficients are computed from the wave properties and the ambient plasma data obtained by the Van Allen Probes with a resolution of 8 hours and 0.1 L-shell. Loss rates follow a complex dynamic structure, imposed by the wave and plasma properties. Hiss effects can be strong, with minimum lifetimes (of ~1 day) moving from energies of ~100 keV at L~5 up to ~2 ...

Ripoll, J.-F.; Santol?k, O.; Reeves, G.; Kurth, W.; Denton, M.; Loridan, V.; Thaller, S.; Kletzing, C.; Turner, D.;

YEAR: 2017     DOI: 10.1002/2017JA024139

diffusion coefficients; electron lifetimes; energy-structure; Radiation belts; Van Allen Probes; Whistler-mode hiss

Energetic electron precipitation and auroral morphology at the substorm recovery phase

It is well known that auroral patterns at the substorm recovery phase are characterized by diffuse or patch structures with intensity pulsation. According to satellite measurements and simulation studies, the precipitating electrons associated with these aurorae can reach or exceed energies of a few hundreds of keV through resonant wave-particle interactions in the magnetosphere. However, because of difficulty of simultaneous measurements, the dependency of energetic electron precipitation (EEP) on auroral morphological chan ...

Oyama, S.; Kero, A.; Rodger, C.; Clilverd, M.; Miyoshi, Y.; Partamies, N.; Turunen, E.; Raita, T.; Verronen, P.; Saito, S.;

YEAR: 2017     DOI: 10.1002/2016JA023484

auroral patch; EEP; Ionosphere; plasma wave; recovery phase; substorm; Van Allen Probes

Generation of lower and upper bands of electrostatic electron cyclotron harmonic waves in the Van Allen radiation belts

Electrostatic electron cyclotron harmonic (ECH) waves generated by the electron loss cone distribution can produce efficient scattering loss of plasma sheet electrons, which has a significant effect on the dynamics in the outer magnetosphere. Here we report two ECH emission events around the same location Lā‰ˆ 5.7\textendash5.8, MLT ā‰ˆ 12 from Van Allen Probes on 11 February (event A) and 9 January 2014 (event B), respectively. The spectrum of ECH waves was centered at the lower half of the harmonic bands during event A, bu ...

Zhou, Qinghua; Xiao, Fuliang; Yang, Chang; Liu, Si; He, Yihua; Baker, D.; Spence, H.; Reeves, G.; Funsten, H.;

YEAR: 2017     DOI: 10.1002/2017GL073051

ECH waves; RBSP results; Van Allen Probes; Wave-particle interaction

Ion Bernstein instability as a possible source for oxygen ion cyclotron harmonic waves

This paper demonstrates that an ion Bernstein instability can be a possible source for recently reported electromagnetic waves with frequencies at or near the singly ionized oxygen ion cyclotron frequency, inline image, and its harmonics. The particle measurements during strong wave activity revealed a relatively high concentration of oxygen ions (\~15\%) whose phase space density exhibits a local peak at energy \~20 keV. Given that the electron plasma-to-cyclotron frequency ratio is inline image, this energy corresponds t ...

Min, Kyungguk; Denton, Richard; Liu, Kaijun; Gary, Peter; Spence, Harlan;

YEAR: 2017     DOI: 10.1002/2017JA023979

O+ Bernstein instability; O+ harmonic waves; O+ ring distribution; Van Allen Probes

Radiation belt seed population and its association with the relativistic electron dynamics: A statistical study

Using the particle data measured by Van Allen Probe A from October 2012 to March 2016, we investigate in detail the radiation belt seed population and its association with the relativistic electron dynamics during 74 geomagnetic storms. The period of the storm recovery phase was limited to 72 h. The statistical study shows that geomagnetic storms and substorms play important roles in the radiation belt seed population (336 keV electrons) dynamics. Based on the flux changes of 1 MeV electrons before and after the storm peak, ...

Tang, C.; Wang, Y.; Ni, B.; Zhang, J.-C.; Reeves, G.; Su, Z.; Baker, D.; Spence, H.; Funsten, H.; Blake, J.;

YEAR: 2017     DOI: 10.1002/2017JA023905

relativistic electrons; Substorm Injections; the outer radiation belt; the seed population; Van Allen Probes

Relativistic electron\textquoterights butterfly pitch angle distribution modulated by localized background magnetic field perturbation driven by hot ring current ions

Dayside modulated relativistic electron\textquoterights butterfly pitch angle distributions (PADs) from \~200 keV to 2.6 MeV were observed by Van Allen Probe B at L = 5.3 on 15 November 2013. They were associated with localized magnetic dip driven by hot ring current ion (60\textendash100 keV proton and 60\textendash200 keV helium and oxygen) injections. We reproduce the electron\textquoterights butterfly PADs at satellite\textquoterights location using test particle simulation. The simulation results illustrate that a negat ...

Xiong, Ying; Chen, Lunjin; Xie, Lun; Fu, Suiyan; Xia, Zhiyang; Pu, Zuyin;

YEAR: 2017     DOI: 10.1002/2017GL072558

butterfly distribution; Radiation belt; ring current; Van Allen Probes

Space Weather Research: Earth\textquoterights Radiation Belts

Fundamental research on Earth\textquoterights space radiation environment is essential for the design and the operations of modern technologies \textendash for communications, weather, navigation, national security \textendash that fly in the hostile space weather conditions above Earth\textquoterights atmosphere. As the technologies become ever more advanced, more sophisticated understanding \textendash and even predictability \textendash of the environment is required for mission success

Lanzerotti, Louis; Baker, Daniel;

YEAR: 2017     DOI: 10.1002/2017SW001654

Earth\textquoterights radiation belts; Space Weather Research; Van Allen Probes

Spatial dependence of electromagnetic ion cyclotron waves triggered by solar wind dynamic pressure enhancements

In this paper, using the multisatellite (the Van Allen Probes and two GOES satellites) observations in the inner magnetosphere, we examine two electromagnetic ion cyclotron (EMIC) wave events that are triggered by Pdyn enhancements under prolonged northward interplanetary magnetic field quiet time preconditions. For both events, the impact of enhanced Pdyn causes EMIC waves at multiple points. However, we find a strong spatial dependence that EMIC waves due to enhanced Pdyn impact can occur at multiple points (likely globall ...

Cho, J.-H.; Lee, D.-Y.; Noh, S.-J.; Kim, H.; Choi, C.; Lee, J.; Hwang, J.;

YEAR: 2017     DOI: 10.1002/2016JA023827

Dynamic pressure; EMIC waves; Van Allen Probes

Dependence of the amplitude of magnetosonic waves on the solar wind and AE index using Van Allen Probes

We present the dependence of the magnetosonic wave amplitudes both outside and inside the plasmapause on the solar wind and AE index using Van Allen Probe-A spacecraft during the time period of 1 October 2012 to 31 December 2015, based on a correlation and regression analysis. Solar wind parameters considered are the southward interplanetary magnetic field (IMF BS), solar wind number density (NSW), and bulk speed (VSW). We find that the wave amplitudes outside (inside) the plasmapause are well correlated with the preceding A ...

Kim, Kyung-Chan; Shprits, Yuri;

YEAR: 2017     DOI: 10.1002/2017JA024094

magnetosonic equatorial noise; solar wind dependence; Van Allen Probes

Electron-acoustic solitons and double layers in the inner magnetosphere

The Van Allen Probes observe generally two types of electrostatic solitary waves (ESW) contributing to the broadband electrostatic wave activity in the nightside inner magnetosphere. ESW with symmetric bipolar parallel electric field are electron phase space holes. The nature of ESW with asymmetric bipolar (and almost unipolar) parallel electric field has remained puzzling. To address their nature, we consider a particular event observed by Van Allen Probes to argue that during the broadband wave activity electrons with ener ...

. Y. Vasko, I; Agapitov, O.; Mozer, F.; Bonnell, J.; Artemyev, A.; Krasnoselskikh, V.; Reeves, G.; Hospodarsky, G.;

YEAR: 2017     DOI: 10.1002/2017GL074026

double layers; electron-acoustic waves; inner magnetosphere; solitons; Van Allen Probes

Global observations of magnetospheric high- m poloidal waves during the 22 June 2015 magnetic storm

We report global observations of high-m poloidal waves during the recovery phase of the 22 June 2015 magnetic storm from a constellation of widely spaced satellites of five missions including Magnetospheric Multiscale (MMS), Van Allen Probes, Time History of Events and Macroscale Interactions during Substorm (THEMIS), Cluster, and Geostationary Operational Environmental Satellites (GOES). The combined observations demonstrate the global spatial extent of storm time poloidal waves. MMS observations confirm high azimuthal wave ...

Le, G.; Chi, P.; Strangeway, R.; Russell, C.; Slavin, J.; Takahashi, K.; Singer, H.; Anderson, B.; Bromund, K.; Fischer, D.; Kepko, E.; Magnes, W.; Nakamura, R.; Plaschke, F.; Torbert, R.;

YEAR: 2017     DOI: 10.1002/2017GL073048

field line resonances; high-m poloidal waves; magnetic storm; magnetospheric multiscale mission; ULF waves; Van Allen Probes

A multi-spacecraft event study of Pc5 ultra low frequency waves in the magnetosphere and their external drivers

We investigate a quiet-time event of magnetospheric Pc5 ultra low frequency (ULF) waves and their likely external drivers using multiple spacecraft observations. Enhancements of electric and magnetic field perturbations in two narrow frequency bands, 1.5-2 mHz and 3.5-4 mHz, were observed over a large radial distance range from r ~5 to 11 RE. During the first half of this event, perturbations were mainly observed in the transverse components and only in the 3.5-4 mHz band. In comparison, enhancements were stronger during the ...

Wang, Chih-Ping; Thorne, Richard; Liu, Terry; Hartinger, Michael; Nagai, Tsugunobu; Angelopoulos, Vassilis; Wygant, John; Breneman, Aaron; Kletzing, Craig; Reeves, Geoffrey; Claudepierre, Seth; Spence, Harlan;

YEAR: 2017     DOI: 10.1002/2016JA023610

IMF discontinuity; inner magnetosphere; Kelvin-Helmholtz vortices; magnetosheath; Pc5 waves; plasma sheet; Van Allen Probes

Propagation characteristics of plasmaspheric hiss: Van Allen Probe observations and global empirical models

Based on the Van Allen Probe A observations from 1 October 2012 to 31 December 2014, we develop two empirical models to respectively describe the hiss wave normal angle (WNA) and amplitude variations in the Earth\textquoterights plasmasphere for different substorm activities. The long-term observations indicate that the plasmaspheric hiss amplitudes on the dayside increase when substorm activity is enhanced (AE index increases), and the dayside hiss amplitudes are greater than the nightside. However, the propagation angles ( ...

Yu, J.; . Y. Li, L; Cao, J.; Chen, L.; Wang, J.; Yang, J.;

YEAR: 2017     DOI: 10.1002/2016JA023372

hiss amplitude model; hiss wave amplitude; Plasmaspheric Hiss; propagation angle model of hiss waves; substorm dependence; Van Allen Probes; wave normal angle

Roles of whistler-mode waves and magnetosonic waves in changing the outer radiation belt and the slot region

Using the Van Allen Probe long-term (2013 \textendash 2015) observations and quasi-linear simulations of wave-particle interactions, we examine the combined or competing effects of whistler-mode waves (chorus or hiss) and magnetosonic (MS) waves on energetic (<0.5 MeV) and relativistic (>0.5 MeV) electrons inside and outside the plasmasphere. Although whistler-mode chorus waves and MS waves can singly or jointly accelerate electrons from the hundreds of keV energy to the MeV energy in the low-density trough, most of the rela ...

. Y. Li, L; Yu, J.; Cao, J.; . Y. Yang, J; Li, X.; Baker, D.; Reeves, G.; Spence, H.;

YEAR: 2017     DOI: 10.1002/2016JA023634

magnetosonic waves; Plasmapause movement; Spatial variation of outer radiaton belt; Spatial variation of slot region; Temporal-spatial variations of chorus waves; Temporal-spatial variations of plasmaspheric hiss; Van Allen Probes

Spatial Scale and Duration of One Microburst Region on 13 August 2015

Prior studies of microburst precipitation have largely relied on estimates of the spatial scale and temporal duration of the microburst region in order to determine the radiation belt loss rate of relativistic electrons. These estimates have often relied on the statistical distribution of microburst events. However, few studies have directly observed the spatial and temporal evolution of a single microburst event. In this study, we combine BARREL balloon-borne X-ray measurements with FIREBIRD-II and AeroCube-6 CubeSat electr ...

Anderson, B.; Shekhar, S.; Millan, R.; Crew, A.; Spence, H.; Klumpar, D.; Blake, J.; O\textquoterightBrien, T.; Turner, D.;

YEAR: 2017     DOI: 10.1002/2016JA023752

Microbursts; Radiation Belt Dynamics; Van Allen Probes; whistler mode chorus waves

Variations of the relativistic electron flux after a magnetospheric compression event

On January 21, 2015, a sharp increase of the solar wind dynamic pressure impacted the magnetosphere. The magnetopause moved inward to the region L< 8 without causing a geomagnetic storm. The flux of the relativistic electrons in the outer radiation belt decreased by half during this event based on the observations of the particle radiation monitor (PRM) of the fourth of the China-Brazil Earth Resource Satellites (CBERS-4). The flux remained low for approximately 11 d; it did not recover after a small magnetic storm on Januar ...

Chen, Zhe; Chen, HongFei; Li, YiFan; Xiang, HongWen; Yu, XiangQian; Shi, WeiHong; Hao, ZhiHua; Zou, Hong; Zou, JiQing; Zhong, WeiYing;

YEAR: 2017     DOI: 10.1007/s11431-016-9008-3

outer radiation belt high-energy electrons medium-energy electrons space environment; Van Allen Probes

Bayesian Spectral Analysis of Chorus Sub-Elements from the Van Allen Probes

We develop a Bayesian spectral analysis technique that calculates the probability distribution functions of a superposition of wave-modes each described by a linear growth rate, a frequency and a chirp rate. The Bayesian framework has a number of advantages, including 1) reducing the parameter space by integrating over the amplitude and phase of the wave, 2) incorporating the data from each channel to determine the model parameters such as frequency which leads to high resolution results in frequency and time, 3) the ability ...

Crabtree, Chris; Tejero, Erik; Ganguli, Gurudas; Hospodarsky, George; Kletzing, Craig;

YEAR: 2017     DOI: 10.1002/2016JA023547

Bayesian Spectral; Chorus; Van Allen Probes; whistler

Generation of extremely low frequency chorus in Van Allen radiation belts

Recent studies have shown that chorus can efficiently accelerate the outer radiation belt electrons to relativistic energies. Chorus, previously often observed above 0.1 equatorial electron gyrofrequency fce, was generated by energetic electrons originating from Earth\textquoterights plasma sheet. Chorus below 0.1 fce has seldom been reported until the recent data from Van Allen Probes, but its origin has not been revealed so far. Because electron resonant energy can approach the relativistic level at extremely low frequency ...

Xiao, Fuliang; Liu, Si; Tao, Xin; Su, Zhenpeng; Zhou, Qinghua; Yang, Chang; He, Zhaoguo; He, Yihua; Gao, Zhonglei; Baker, D.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.;

YEAR: 2017     DOI: 10.1002/2016JA023561

ELF chorus waves; RBSP results; relativistic distribution; Van Allen Probes; Wave-particle interaction

The hidden dynamics of relativistic electrons (0.7-1.5~MeV) in the inner zone and slot region

We present measurements of relativistic electrons (0.7\textendash1.5 MeV) in the inner zone and slot region obtained by the Magnetic Electron and Ion Spectrometer (MagEIS) instrument on Van Allen Probes. The data presented are corrected for background contamination, which is primarily due to inner-belt protons in these low-L regions. We find that \~1 MeV electrons were transported into the inner zone following the two largest geomagnetic storms of the Van Allen Probes era to date, the March and June 2015 events. As \~1 MeV e ...

Claudepierre, S.; O\textquoterightBrien, T.; Fennell, J.; Blake, J.; Clemmons, J.; Looper, M.; Mazur, J.; Roeder, J.; Turner, D.; Reeves, G.; Spence, H.;

YEAR: 2017     DOI: 10.1002/2016JA023719

Inner zone; particle detectors; Radiation belt; relativistic electrons; Slot region; Space weather; Van Allen Probes

The hidden dynamics of relativistic electrons (0.7-1.5~MeV) in the inner zone and slot region

We present measurements of relativistic electrons (0.7\textendash1.5 MeV) in the inner zone and slot region obtained by the Magnetic Electron and Ion Spectrometer (MagEIS) instrument on Van Allen Probes. The data presented are corrected for background contamination, which is primarily due to inner-belt protons in these low-L regions. We find that \~1 MeV electrons were transported into the inner zone following the two largest geomagnetic storms of the Van Allen Probes era to date, the March and June 2015 events. As \~1 MeV e ...

Claudepierre, S.; O\textquoterightBrien, T.; Fennell, J.; Blake, J.; Clemmons, J.; Looper, M.; Mazur, J.; Roeder, J.; Turner, D.; Reeves, G.; Spence, H.;

YEAR: 2017     DOI: 10.1002/2016JA023719

Inner zone; particle detectors; Radiation belt; relativistic electrons; Slot region; Space weather; Van Allen Probes

An improved sheath impedance model for the Van Allen probes EFW instrument: Effects of the spin axis antenna

A technique to quantitatively determine the sheath impedance of the Van Allen Probes Electric Field and Waves (EFW) instrument is presented. This is achieved, for whistler mode waves, through a comparison between the total electric field wave power spectra calculated from magnetic field observations and cold plasma theory, and the total electric field wave power measured by the EFW spherical double probes instrument. In a previous study, a simple density-dependent sheath impedance model was developed in order to account for ...

Hartley, D.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Bounds, S.; Averkamp, T.; Bonnell, J.; ik, O.; Wygant, J.;

YEAR: 2017     DOI: 10.1002/2016JA023597

antenna sheath impedance; EFW; electric field; EMFISIS; Van Allen Probes; whistler mode waves

Inferring electromagnetic ion cyclotron wave intensity from low altitude POES proton flux measurements: A detailed case study with conjugate Van Allen Probes observations

Zhang, Yang; Shi, Run; Ni, Binbin; Gu, Xudong; Zhang, Xianguo; Zuo, Pingbing; Fu, Song; Xiang, Zheng; Wang, Qi; Cao, Xing; Zou, Zhengyang;

YEAR: 2017     DOI: 10.1016/j.asr.2016.12.035

Van Allen Probes

Ion acceleration at dipolarization fronts in the inner magnetosphere

During geomagnetic storms plasma pressure in the inner magnetosphere is controlled by energetic ions of tens to hundreds of keV. Plasma pressure is the source of global storm time currents, which control the distribution of magnetic field and couple the inner magnetosphere and the ionosphere. Recent analysis showed that the buildup of hot ion population in the inner magnetosphere largely occurs in the form of localized discrete injections associated with sharp dipolarizations of magnetic field, similar to dipolarization fron ...

. Y. Ukhorskiy, A; Sitnov, M.; Merkin, V.; Gkioulidou, M.; Mitchell, D.;

YEAR: 2017     DOI: 10.1002/2016JA023304

injections; ring current; trapping; Van Allen Probes

Location of intense electromagnetic ion cyclotron (EMIC) wave events relative to the plasmapause: Van Allen Probes observations

We have studied the spatial location relative to the plasmapause (PP) of the most intense electromagnetic ion cyclotron (EMIC) waves observed on Van Allen Probes A and B during their first full precession in local time. Most of these waves occurred over an L range of from -1 to +2 RE relative to the PP. Very few events occurred only within 0.1 RE of the PP, and events with a width in L of < 0.2 REoccurred both inside and outside the PP. Wave occurrence was always associated with high densities of ring current ions; plasma de ...

Tetrick, S.; Engebretson, M.; Posch, J.; Olson, C.; Smith, C.; Denton, R.; Thaller, S.; Wygant, J.; Reeves, G.; MacDonald, E.; Fennell, J.;

YEAR: 2017     DOI: 10.1002/2016JA023392

EMIC waves; Magnetosphere; Plasmapause; Van Allen Probes

Oxygen cyclotron harmonic waves observed by the Van Allen Probes

Fine structured multiple-harmonic electromagnetic emissions at frequencies around the equatorial oxygen cyclotron harmonics are observed by Van Allen Probe A outside the core plasmasphere (L~5) off the magnetic equator (MLAT~-7.5\textdegree) during a magnetic storm. We find that the multiple-harmonic emissions have their PSD peaks at 2~8 equatorial oxygen gyro-harmonics (f~nfO+, n=2~8) while the fundamental mode (n=1) is absent, implying that the harmonic waves are generated near the equator and propagate into the observatio ...

Xiongdong, Yu; Zhigang, Yuan; Dedong, Wang; Shiyong, Huang; Haimeng, Li; Tao, Yu; Zheng, Qiao;

YEAR: 2017     DOI: 10.1007/s11430-016-9024-3

Oxygen Cyclotron Harmonic Waves; Radiation belt; Ring current ions; Van Allen Probes

A positive correlation between energetic electron butterfly distributions and magnetosonic waves in the radiation belt slot region

Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly dist ...

Yang, Chang; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; Wang, Shui; Spence, H.; Reeves, G.; Baker, D.; Blake, J.; Funsten, H.;

YEAR: 2017     DOI: 10.1002/2017GL073116

butterfly distributions; Electron acceleration; Landau resonance; magnetosonic wave; Radiation belt; Van Allen Probes; Wave-particle interaction

Second harmonic poloidal waves observed by Van Allen Probes in the dusk-midnight sector

This paper presents observations of ultralow-frequency (ULF) waves from Van Allen Probes. The event that generated the ULF waves occurred 2 days after a minor geomagnetic storm during a geomagnetically quiet time. Narrowband pulsations with a frequency of about 7 mHz with moderate amplitudes were registered in the premidnight sector when Probe A was passing through an enhanced density region near geosynchronous orbit. Probe B, which passed through the region earlier, did not detect the narrowband pulsations but only broadban ...

Min, Kyungguk; Takahashi, Kazue; Ukhorskiy, Aleksandr; Manweiler, Jerry; Spence, Harlan; Singer, Howard; Claudepierre, Seth; Larsen, Brian; Soto-Chavez, Rualdo; Cohen, Ross;

YEAR: 2017     DOI: 10.1002/2016JA023770

drift-bounce resonance; high m ULF waves; Second harmonic poloidal mode; Van Allen Probes

Simultaneous event-specific estimates of transport, loss, and source rates for relativistic outer radiation belt electrons

The most significant unknown regarding relativistic electrons in Earth\textquoterights outer Van Allen radiation belt is the relative contribution of loss, transport, and acceleration processes within the inner magnetosphere. Detangling each individual process is critical to improve the understanding of radiation belt dynamics, but determining a single component is challenging due to sparse measurements in diverse spatial and temporal regimes. However, there are currently an unprecedented number of spacecraft taking measurem ...

Schiller, Q.; Tu, W.; Ali, A.; Li, X.; Godinez, H.; Turner, D.; Morley, S.; Henderson, M.;

YEAR: 2017     DOI: 10.1002/2016JA023093

CubeSat; data assimilation; electron; event specific; Modeling; Radiation belt; Van Allen Probes

Ultra-relativistic radiation belt extinction and ULF wave radial diffusion: Modeling the September 2014 extended dropout event

In September 2014 an unusually long-lasting (ā‰³10 days) ultra-relativistic electron flux depletion occurred in the outer radiation belt despite ongoing solar wind forcing. We simulate this period using a ULF wave radial diffusion model, driven by observed ULF wave power coupled to flux variations at the outer boundary at L* = 5, including empirical electron loss models due to chorus and hiss wave scattering. Our results show that unexplained rapid main phase loss, that depletes the belt within hours, is essential to explain ...

Ozeke, Louis; Mann, Ian; Murphy, Kyle; Sibeck, David; Baker, Daniel;

YEAR: 2017     DOI: 10.1002/2017GL072811

radial diffusion; Radiation belt; ULF waves; ultrarelativistic; Van Allen Probes; wave-particle interactions

Van Allen Probes observations of structured whistler mode activity and coincident electron Landau acceleration inside a remnant plasmaspheric plume

We present observations from the Van Allen Probes spacecraft that identify a region of intense whistler mode activity within a large density enhancement outside of the plasmasphere. We speculate that this density enhancement is part of a remnant plasmaspheric plume, with the observed wave being driven by a weakly anisotropic electron injection that drifted into the plume and became nonlinearly unstable to whistler emission. Particle measurements indicate that a significant fraction of thermal (<100 eV) electrons within the p ...

Woodroffe, J.; Jordanova, V.; Funsten, H.; Streltsov, A.; Bengtson, M.; Kletzing, C.; Wygant, J.; Thaller, S.; Breneman, A.;

YEAR: 2017     DOI: 10.1002/2015JA022219

Ducting; Van Allen Probes; wave-particle interactions; Whistlers

Analysis of self-consistent nonlinear wave-particle interactions of whistler waves in laboratory and space plasmas

Whistler mode chorus is one of the most important emissions affecting the energization of the radiation belts. Recent laboratory experiments that inject energetic electron beams into a cold plasma have revealed several spectral features in the nonlinear evolution of these instabilities that have also been observed in high-time resolution in situ wave-form data. These features include (1) a sub-element structure which consists of an amplitude modulation on time-scales slower than the bounce time, (2) closely spaced discrete f ...

Crabtree, Chris; Ganguli, Gurudas; Tejero, Erik;

YEAR: 2017     DOI: 10.1063/1.4977539

Dispersion relations; Electron beams; SingingEigenvalues; Van Allen Probes; Whistler waves

Chorus whistler wave source scales as determined from multipoint Van Allen Probe measurements

Whistler mode chorus waves are particularly important in outer radiation belt dynamics due to their key role in controlling the acceleration and scattering of electrons over a very wide energy range. The key parameters for both nonlinear and quasi-linear treatment of wave-particle interactions are the temporal and spatial scales of the wave source region and coherence of the wave field perturbations. Neither the source scale nor the coherence scale is well established experimentally, mostly because of a lack of multipoint VL ...

Agapitov, O.; Blum, L.; Mozer, F.; Bonnell, J.; Wygant, J.;

YEAR: 2017     DOI: 10.1002/2017GL072701

chorus spatial scales; Van Allen Probes; VLF waves

Comparing and contrasting dispersionless injections at geosynchronous orbit during a substorm event

Particle injections in the magnetosphere transport electrons and ions from the magnetotail to the radiation belts. Here we consider generation mechanisms of \textquotedblleftdispersionless\textquotedblright injections, namely, those with simultaneous increase of the particle flux over a wide energy range. In this study we take advantage of multisatellite observations which simultaneously monitor Earth\textquoterights magnetospheric dynamics from the tail toward the radiation belts during a substorm event. Dispersionless inje ...

Kronberg, E.; Grigorenko, E.; Turner, D.; Daly, P.; Khotyaintsev, Y.; Kozak, L.;

YEAR: 2017     DOI: 10.1002/2016JA023551

Acceleration; current wedge; Dipolarization; particle injections; substorm; ULF waves; Van Allen Probes

Diffusive scattering of electrons by electron holes around injection fronts

Van Allen Probes have detected nonlinear electrostatic spikes around injection fronts in the outer radiation belt. These spikes include electron holes (EH), double layers, and more complicated solitary waves. We show that EHs can efficiently scatter electrons due to their substantial transverse electric fields. Although the electron scattering driven by EHs is diffusive, it cannot be evaluated via the standard quasi-linear theory. We derive analytical formulas describing local electron scattering by a single EH and verify th ...

. Y. Vasko, I; Agapitov, O.; Mozer, F.; Artemyev, A.; Krasnoselskikh, V.; Bonnell, J.;

YEAR: 2017     DOI: 10.1002/2016JA023337

electron holes; electron losses; injection; Radiation belt; solitary waves; Van Allen Probes

On the origin of low-energy electrons in the inner magnetosphere: Fluxes and pitch-angle distributions

Accurate knowledge of the plasma fluxes in the inner magnetosphere is essential for both scientific and programmatic applications. Knowledge of the low-energy electrons (approximately tens to hundreds of eV) in the inner magnetosphere is particularly important since these electrons are acted upon by various physical processes, accelerating the electrons to higher energies, and also causing their loss. However, measurements of low-energy electrons are challenging, and as a result, this population has been somewhat neglected p ...

Denton, M.; Reeves, G.; Larsen, B.; Friedel, R.; Thomsen, M.; Fernandes, P.; Skoug, R.; Funsten, H.; Sarno-Smith, L.;

YEAR: 2017     DOI: 10.1002/2016JA023648

inner magnetosphere; Van Allen Probes

The role of the convection electric field in filling the slot region between the inner and outer radiation belts

The Van Allen Probes have reported frequent flux enhancements of 100s keV electrons in the slot region, with lower energy electrons exhibiting more dynamic behavior at lower L shells. Also, in situ electric field measurements from the Combined Release and Radiation Effects Satellite, Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Van Allen Probes have provided evidence for large-scale electric fields at low L shells during active times. We study an event on 19 February 2014 where hundre ...

Califf, S.; Li, X.; Zhao, H.; Kellerman, A.; Sarris, T.; Jaynes, A.; Malaspina, D.;

YEAR: 2017     DOI: 10.1002/2016JA023657

convection; electric field; electrons; Slot region; Van Allen Probes

Second harmonic poloidal waves observed by Van Allen Probes in the dusk-midnight sector

This paper presents observations of ultra-low frequency (ULF) waves from Van Allen Probes. The event that generated the ULF waves occurred two days after a minor geomagnetic storm during a geomagnetically quiet time. Narrowband pulsations with a frequency of about 7 mHz with moderate amplitudes were registered in the pre-midnight sector when Probe A was passing through an enhanced density region near geosynchronous orbit. Probe B, which passed through the region earlier, did not detect the narrowband pulsations but only broa ...

Min, Kyungguk; Takahashi, Kazue; Ukhorskiy, Aleksandr; Manweiler, Jerry; Spence, Harlan; Singer, Howard; Claudepierre, Seth; Larsen, Brian; Soto-Chavez, Rualdo; Cohen, Ross;

YEAR: 2017     DOI: 10.1002/2016JA023770

drift-bounce resonance; high m ULF waves; Second harmonic poloidal mode; Van Allen Probes

Transverse eV ion heating by random electric field fluctuations in the plasmasphere

Charged particle acceleration in the Earth inner magnetosphere is believed to be mainly due to the local resonant wave-particle interaction or particle transport processes. However, the Van Allen Probes have recently provided interesting evidence of a relatively slow transverse heating of eV ions at distances about 2\textendash3 Earth radii during quiet times. Waves that are able to resonantly interact with such very cold ions are generally rare in this region of space, called the plasmasphere. Thus, non-resonant wave-partic ...

Artemyev, A.; Mourenas, D.; Agapitov, O.; Blum, L.;

YEAR: 2017     DOI: 10.1063/1.4976713

electric fields; Electrostatic Waves; protons; Van Allen Probes; Wave power; Whistler waves

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 ultralow frequency (ULF) waves on 29 October 2013. Oscillations in electron flux were observed at the period of \~450 s, 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, J.; Kletzing, C.;

YEAR: 2017     DOI: 10.1002/2016GL071252

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

Van Allen Probes Observations of Structured Whistler-mode Activity and Coincident Electron Landau Acceleration Inside a Remnant Plasmaspheric Plume

We present observations from the Van Allen Probes spacecraft that identify an region of intense whistler-mode activity within a large density enhancement outside of the plasmasphere. We speculate that this density enhancement is part of a remnant plasmaspheric plume, with the observed wave being driven by a weakly anisotropic electron injection that drifted into the plume and became non-linearly unstable to whistler emission. Particle measurements indicate that a significant fraction of thermal (<100 eV) electrons within the ...

Woodroffe, J.; Jordanova, V.; Funsten, H.; Streltsov, A.; Bengtson, M.; Kletzing, C.; Wygant, J.; Thaller, S.; Breneman, A.;

YEAR: 2017     DOI: 10.1002/2015JA022219

Ducting; Van Allen Probes; wave-particle interactions; Whistlers

Amplitude\textendashfrequency characteristics of ion\textendashcyclotron and whistler-mode waves from Van Allen Probes data

Using two-hour (from 2300 UT January 25, 2013 to 0100 UT January 26, 2013) measurement data from Van Allen Probes on fluxes of energetic particles, cold plasma density, and magnetic field magnitude, we have calculated the local growth rate of electromagnetic ion\textendashcyclotron and whistler-mode waves for field-aligned propagation. The results of these calculations have been compared with wave spectra observed by the same Van Allen Probe spacecraft. The time intervals when the calculated wave increments are sufficiently ...

Lyubchich, A.; Demekhov, A.; Titova, E.; Yahnin, A.;

YEAR: 2017     DOI: 10.1134/S001679321701008X

Van Allen Probes

Coherently modulated whistler mode waves simultaneously observed over unexpectedly large spatial scales

Utilizing simultaneous twin Van Allen Probes observations of whistler mode waves at variable separations, we are able to distinguish the temporal variations from spatial variations, determine the coherence spatial scale, and suggest the possible mechanism of wave modulation. The two probes observed coherently modulated whistler mode waves simultaneously at an unexpectedly large distance up to ~4.3 RE over 3 h during a relatively quiet period. The modulation of 150\textendash500 Hz plasmaspheric hiss was correlated with whist ...

Li, Jinxing; Bortnik, Jacob; Li, Wen; Thorne, Richard; Ma, Qianli; Chu, Xiangning; Chen, Lunjin; Kletzing, Craig; Kurth, William; Hospodarsky, George; Wygant, John; Breneman, Aaron; Thaller, Scott;

YEAR: 2017     DOI: 10.1002/2016JA023706

coherent waves; multisatellite; periodic rising tone; Van Allen Probes; whistler mode

Coherently modulated whistler mode waves simultaneously observed over unexpectedly large spatial scales

Utilizing simultaneous twin Van Allen Probes observations of whistler mode waves at variable separations, we are able to distinguish the temporal variations from spatial variations, determine the coherence spatial scale, and suggest the possible mechanism of wave modulation. The two probes observed coherently modulated whistler mode waves simultaneously at an unexpectedly large distance up to ~4.3 RE over 3 h during a relatively quiet period. The modulation of 150\textendash500 Hz plasmaspheric hiss was correlated with whist ...

Li, Jinxing; Bortnik, Jacob; Li, Wen; Thorne, Richard; Ma, Qianli; Chu, Xiangning; Chen, Lunjin; Kletzing, Craig; Kurth, William; Hospodarsky, George; Wygant, John; Breneman, Aaron; Thaller, Scott;

YEAR: 2017     DOI: 10.1002/2016JA023706

coherent waves; multisatellite; periodic rising tone; Van Allen Probes; whistler mode

EMIC wave scale size in the inner magnetosphere: Observations from the dual Van Allen Probes

Estimating the spatial scales of electromagnetic ion cyclotron (EMIC) waves is critical for quantifying their overall scattering efficiency and effects on thermal plasma, ring current, and radiation belt particles. Using measurements from the dual Van Allen Probes in 2013\textendash2014, we characterize the spatial and temporal extents of regions of EMIC wave activity and how these depend on local time and radial distance within the inner magnetosphere. Observations are categorized into three types\textemdashwaves observed b ...

Blum, L.; Bonnell, J.; Agapitov, O.; Paulson, K.; Kletzing, C.;

YEAR: 2017     DOI: 10.1002/2016GL072316

EMIC waves; inner magnetosphere; multipoint; spatial scales; 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 ultralow frequency (ULF) waves. The waves exhibited strong spectral power in the 5\textendash40 mHz band and included multiharmonic toroidal waves visible up to the eleventh 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 U ...

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

YEAR: 2017     DOI: 10.1002/2014JA020373

multispacecraft observation; plasmasphere; ULF waves; Van Allen Probes



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