Bibliography



Found 938 entries in the Bibliography.


Showing entries from 551 through 600


2015

Source and Seed Populations for Relativistic Electrons: Their Roles in Radiation Belt Changes

Strong enhancements of outer Van Allen belt electrons have been shown to have a clear dependence on solar wind speed and on the duration of southward interplanetary magnetic field. However, individual case study analyses also have demonstrated that many geomagnetic storms produce little in the way of outer belt enhancements and, in fact, may produce substantial losses of relativistic electrons. In this study, focused upon a key period in August-September 2014, we use GOES geostationary orbit electron flux data and Van Allen ...

Jaynes, A.N.; Baker, D.N.; Singer, H.J.; Rodriguez, J.V.; Loto\textquoterightaniu, T.M.; Ali, A.; Elkington, S.R.; Li, X.; Kanekal, S.G.; Fennell, J.F.; Li, W.; Thorne, R.M.; Kletzing, C.A.; Spence, H.E.; Reeves, G.D.;

YEAR: 2015     DOI: 10.1002/2015JA021234

Radiation belts; relativistic electrons; substorms; ULF waves; Van Allen Probes; VLF waves

Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities

We report correlated data on nightside chorus waves and energetic electrons during two small storm periods: 1 November 2012 (Dst≈-45) and 14 January 2013 (Dst≈-18). The Van Allen Probes simultaneously observed strong chorus waves at locations L = 5.8 - 6.3, with a lower frequency band 0.1 - 0.5fce and a peak spectral density \~[10-4 nT2/Hz. In the same period, the fluxes and anisotropy of energetic (\~ 10-300 keV) electrons were greatly enhanced in the interval of large negative interplanetary magnetic field Bz. Using a ...

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

YEAR: 2015     DOI: 10.1002/2015JA021376

chorus wave excitation; energetic electrons; Geomagnetic storm; Van Allen Probes; Van Allen probes results; Wave-particle interaction

Correlated Pc4-5 ULF waves, whistler-mode chorus and pulsating aurora observed by the Van Allen Probes and ground-based systems

Theory and observations have linked equatorial VLF waves with pulsating aurora for decades, invoking the process of pitch-angle scattering of 10\textquoterights keV electrons in the equatorial magnetosphere. Recently published satellite studies have strengthened this argument, by showing strong correlation between pulsating auroral patches and both lower-band chorus and 10\textquoterights keV electron modulation in the vicinity of geosynchronous orbit. Additionally, a previous link has been made between Pc4-5 compressional p ...

Jaynes, A.; Lessard, M.; Takahashi, K.; Ali, A.; Malaspina, D.; Michell, R.; Spanswick, E.; Baker, D.; Blake, J.; Cully, C.; Donovan, E.; Kletzing, C.; Reeves, G.; Samara, M.; Spence, H.; Wygant, J.;

YEAR: 2015     DOI: 10.1002/2015JA021380

aurora; precipitation; pulsating aurora; substorms; ULF waves; Van Allen Probes; VLF waves

Dense plasma and Kelvin-Helmholtz waves at Earth\textquoterights dayside magnetopause

Spacecraft observations of boundary waves at the dayside terrestrial magnetopause and their ground-based signatures are presented. Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft measured boundary waves at the magnetopause while ground-based HF radar measured corresponding signatures in the ionosphere indicating a large-scale response and tailward propagating waves. The properties of the oscillations are consistent with linear phase Kelvin-Helmholtz waves along the magnetopause boundar ...

Walsh, B.; Thomas, E.; Hwang, K.-J.; Baker, J.; Ruohoniemi, J.; Bonnell, J.;

YEAR: 2015     DOI: 10.1002/2015JA021014

Kelvin-Helmholtz; magnetopause

The effects of geomagnetic storms on electrons in Earth\textquoterights radiation belts

We use Van Allen Probes data to investigate the responses of 10s of keV to 2 MeV electrons throughout a broad range of the radiation belts (2.5 <= L <= 6.0) during 52 geomagnetic storms from the most recent solar maximum. Electron storm-time responses are highly dependent on both electron energy and L-shell. 10s of keV electrons typically have peak fluxes in the inner belt or near-Earth plasma sheet and fill the inner magnetosphere during storm main phases. ~100 to ~600 keV electrons are enhanced in up to 87\% of cases aroun ...

Turner, D.; O\textquoterightBrien, T.; Fennell, J.; Claudepierre, S.; Blake, J.; Kilpua, E.; Hietala, H.;

YEAR: 2015     DOI: 10.1002/2015GL064747

electrons; Van Allen Probes; Geomagnetic storms; Radiation belts

Extreme geomagnetic disturbances due to shocks within CMEs

We report on features of solar wind-magnetosphere coupling elicited by shocks propagating through coronal mass ejections (CMEs) by analyzing the intense geomagnetic storm of 6 August 1998. During this event, the dynamic pressure enhancement at the shock combined with a simultaneous increase in the southward component of the magnetic field resulted in a large earthward retreat of Earth\textquoterights magnetopause, which remained close to geosynchronous orbit for more than 4 h. This occurred despite the fact that both shock a ...

Lugaz, N.; Farrugia, C.; Huang, C.-L.; Spence, H.;

YEAR: 2015     DOI: 10.1002/2015GL064530

coronal mass ejections; Geomagnetic storm; magnetopause; magnetosheath; shocks

Global-scale coherence modulation of radiation-belt electron loss from plasmaspheric hiss

Over 40 years ago it was suggested that electron loss in the region of the radiation belts that overlaps with the region of high plasma density called the plasmasphere, within four to five Earth radii1, 2, arises largely from interaction with an electromagnetic plasma wave called plasmaspheric hiss3, 4, 5. This interaction strongly influences the evolution of the radiation belts during a geomagnetic storm, and over the course of many hours to days helps to return the radiation-belt structure to its \textquoteleftquiet\textqu ...

Breneman, A.; Halford, A.; Millan, R.; McCarthy, M.; Fennell, J.; Sample, J.; Woodger, L.; Hospodarsky, G.; Wygant, J.; Cattell, C.; Goldstein, J.; Malaspina, D.; Kletzing, C.;

YEAR: 2015     DOI: 10.1038/nature14515

Magnetospheric physics; Van Allen Probes

Nonlinear Bounce Resonances between Magnetosonic Waves and Equatorially Mirroring Electrons

Equatorially mirroring energetic electrons pose an interesting scientific problem, since they generally cannot resonate with any known plasma waves and hence cannot be scattered down to lower pitch angles. Observationally it is well known that the fluxof these equatorial particles does not simply continue to build up indefinitely, and so a mechanism must necessarily exist that transports these particles from a equatorial pitch angle of 90 degrees down to lower values. However this mechanism has not been uniquely identified y ...

Chen, Lunjin; Maldonado, Armando; Bortnik, Jacob; Thorne, Richard; Li, Jinxing; Dai, Lei; Zhan, Xiaoya;

YEAR: 2015     DOI: 10.1002/2015JA021174

bounce resonance; equatorioal noise; magnetosonic waves; nonlinear; Radiation belt; wave particle interaction

Relativistic electron precipitations in association with diffuse aurora: Conjugate observation of SAMPEX and the all sky TV camera at Syowa Station

It has been believed that whistler mode waves can cause relativistic electron precipitations. It has been also pointed out that pitch angle scattering of ~keV electrons by whistler mode waves results in diffuse auroras. Thus, it is natural to expect relativistic electron precipitations associated with diffuse auroras. Based on a conjugate observation between the SAMPEX spacecraft and the all-sky TV camera at Syowa Station, we report, for the first time, a case in which relativistic electron precipitations are associated with ...

Kurita, Satoshi; Kadokura, Akira; Miyoshi, Yoshizumi; Morioka, Akira; Sato, Yuka; Misawa, Hiroaki;

YEAR: 2015     DOI: 10.1002/2015GL064564

diffuse aurora; Radiation belts; SAMPEX; Syowa Station; whistler mode wave

Relativistic electron scattering by magnetosonic waves: Effects of discrete wave emission and high wave amplitudes

In this paper, we study relativistic electron scattering by fast magnetosonic waves. We compare results of test particle simulations and the quasi-linear theory for different spectra of waves to investigate how a fine structure of the wave emission can influence electron resonant scattering. We show that for a realistically wide distribution of wave normal angles theta (i.e., when the dispersion delta theta >= 0.5 degrees), relativistic electron scattering is similar for a wide wave spectrum and for a spectrum consisting in ...

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

YEAR: 2015     DOI: 10.1063/1.4922061

chorus waves; CLUSTER SPACECRAFT; equatorial noise; MAGNETIC-FIELD; PLASMA; Quasi-linear diffusion; radiation belt electrons; RESONANT SCATTERING; Van Allen Probes; WHISTLER-MODE WAVES

A statistical study of EMIC waves observed by Cluster: 1. Wave properties

Electromagnetic ion cyclotron (EMIC) waves are an important mechanism for particle energization and losses inside the magnetosphere. In order to better understand the effects of these waves on particle dynamics, detailed information about the occurrence rate, wave power, ellipticity, normal angle, energy propagation angle distributions, as well as local plasma parameters are required. Previous statistical studies have used in situ observations to investigate the distribution of these parameters in the MLT-L frame within a li ...

Allen, R.; Zhang, J.; Kistler, L.; Spence, H.; Lin, R.; Klecker, B.; Dunlop, M.; e, Andr\; Jordanova, V.;

YEAR: 2015     DOI: 10.1002/2015JA021333

Cluster; EMIC waves; Magnetosphere; Shabansky orbits

Van Allen probes, NOAA, GOES, and ground observations of an intense EMIC wave event extending over 12 hours in MLT

Although most studies of the effects of EMIC waves on Earth\textquoterights outer radiation belt have focused on events in the afternoon sector in the outer plasmasphere or plume region, strong magnetospheric compressions provide an additional stimulus for EMIC wave generation across a large range of local times and L shells. We present here observations of the effects of a wave event on February 23, 2014 that extended over 8 hours in UT and over 12 hours in local time, stimulated by a gradual 4-hour rise and subsequent shar ...

Engebretson, M.; Posch, J.; Wygant, J.; Kletzing, C.; Lessard, M.; Huang, C.-L.; Spence, H.; Smith, C.; Singer, H.; Omura, Y.; Horne, R.; Reeves, G.; Baker, D.; Gkioulidou, M.; Oksavik, K.; Mann, I.; Raita, T; Shiokawa, K.;

YEAR: 2015     DOI: 10.1002/2015JA021227

EMIC waves; magnetospheric compressions; Radiation belts; Van Allen Probes

Weak Kinetic Alfv\ en Waves Turbulence during the November 14th 2012 geomagnetic storm: Van Allen Probes observations

n the dawn sector, L~ 5.5 and MLT~4-7, from 01:30 to 06:00 UT during the November 14th 2012 geomagnetic storm, both Van Allen Probes observed an alternating sequence of locally quiet and disturbed intervals with two strikingly different power fluctuation levels and magnetic field orientations: either small (~10-2 nT2) total power with strong GSM Bx and weak By, or large (~10 nT2) total power with weak Bx, and strong By and Bz components. During both kinds of intervals the fluctuations occur in the vicinity of the local ion g ...

Moya, Pablo.; Pinto, V\; Vi\~nas, Adolfo; Sibeck, David; Kurth, William; Hospodarsky, George; Wygant, John;

YEAR: 2015     DOI: 10.1002/2014JA020281

Kinetic Alfven Waves; Magnetic Storms; Radiation belts; Van Allen Probes

3D test-particle simulation of the 17-18 March, 2013 CME-shock driven storm

D test-particle simulation of energetic electrons (hundreds of keV to MeV), including both an initially trapped population and continuously injected population, driven by the Lyon-Fedder-Mobarry (LFM) global MHD model coupled with Magnetosphere-Ionosphere Coupler/Solver (MIX) boundary conditions, is performed for the March 17, 2013 storm. The electron trajectories are calculated and weighted using the ESA model for electron flux vs. energy and L. The simulation captures the flux dropout at both GOES-13 and GOES-15 locations ...

Li, Zhao; Hudson, Mary; Kress, Brian; Paral, Jan;

YEAR: 2015     DOI: 10.1002/2015GL064627

17 March; 2013; CME-shock driven storm; Radiation belt; test-particle simulation

A background correction algorithm for Van Allen Probes MagEIS electron flux measurements

We describe an automated computer algorithm designed to remove background contamination from the Van Allen Probes MagEIS electron flux measurements. We provide a detailed description of the algorithm with illustrative examples from on-orbit data. We find two primary sources of background contamination in the MagEIS electron data: inner zone protons and bremsstrahlung X-rays generated by energetic electrons interacting with the spacecraft material. Bremsstrahlung X-rays primarily produce contamination in the lower energy MagE ...

Claudepierre, S.; O\textquoterightBrien, T.; Blake, J.; Fennell, J.; Roeder, J.; Clemmons, J.; Looper, M.; Mazur, J.; Mulligan, T.; Spence, H.; Reeves, G.; Friedel, R.; Henderson, M.; Larsen, B.;

YEAR: 2015     DOI: 10.1002/2015JA021171

Background contamination; Inner radiation belt; outer radiation belt; Particle measurements; Radiation belt; Spacecraft engineering; Van Allen Probes

The enhancement of cosmic radio noise absorption due to hiss-driven energetic electron precipitation during substorms

The Van-Allen probes, low-altitude NOAA satellite, MetOp satellite and riometer are used to analyze variations of precipitating energetic electron fluxes and cosmic radio noise absorption (CNA) driven by plasmaspheric hiss with respect to geomagnetic activities. The hiss-driven energetic electron precipitations (at L~4.7-5.3, MLT~8-9) are observed during geomagnetic quiet condition and substorms, respectively. We find that the CNA detected by riometers increased very little in the hiss-driven event during quiet condition on ...

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

YEAR: 2015     DOI: 10.1002/2015JA021113

cosmic radio noise absorption; energetic electron precipitation; hiss; substorm; Van Allen Probes

Generation of nonlinear Electric Field Bursts in the outer radiation belt through the parametric decay of whistler waves

Huge numbers of different non-linear structures (double layers, electron holes, non-linear whistlers, etc. referred to as Time Domain Structures - TDS) have been observed by the electric field experiment on the Van Allen Probes. Some of them are associated with whistler waves. Such TDS often emerge on the forward edges of the whistler wave packets and form chains. The parametric decay of a whistler wave into a whistler wave propagating in the opposite direction and an electron acoustic wave is studied experimentally as well ...

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

YEAR: 2015     DOI: 10.1002/2015GL064145

electron acoustic waves; nonlinear structure formation; parametric decay of whistlers; Van Allen Probes

Multipoint observations of the open-closed field line boundary as observed by the Van Allen Probes and geostationary satellites during the November 14 th 2012 geomagnetic storm

The twin Van Allen Probes spacecraft witnessed a series of lobe encounters between 0200 and 0515 UT on November 14th 2012. Although lobe entry had been observed previously by the other spacecraft, the two Van Allen Probe spacecraft allow us to observe the motion of the boundary for the first time. Moreover, this event is unique in that it consists of a series of six quasi-periodic lobe entries. The events occurred on the dawn flank between 4 and 6.6 local time and at altitudes between 5.6 and 6.2 RE. During the events Dst dr ...

Dixon, P.; MacDonald, E.; Funsten, H.; Glocer, A.; Grande, M.; Kletzing, C.; Larsen, B.; Reeves, G.; Skoug, R.; Spence, H.; Thomsen, M.;

YEAR: 2015     DOI: 10.1002/2014JA020883

Lobes; Magnetosphere; Modelling; Open/closed field line boundary; Van Allen Probes

Nonlinear subcyclotron resonance as a formationmechanism for gaps in banded chorus

An interesting characteristic of magnetospheric chorus is the presence of a frequency gap at ω≃0.5Ωe, where Ωe is the electron cyclotron angular frequency. Recent chorus observations sometimes show additional gaps near 0.3Ωe and 0.6Ωe. Here we present a novel nonlinear mechanism for the formation of these gaps using Hamiltonian theory and test particle simulations in a homogeneous, magnetized, collisionless plasma. We find that an oblique whistler wave with frequency at a fraction of the electron cyclotron frequency c ...

Fu, Xiangrong; Guo, Zehua; Dong, Chuanfei; Gary, Peter;

YEAR: 2015     DOI: 10.1002/2015GL064182

banded chorus; nonlinear theory; subcyclotron resonance

Observations of magnetospheric high-m poloidal waves by ST-5 satellites in low Earth orbit during geomagnetically quiet times

The poloidal waves with large azimuthal wavenumbers (m~100) in the magnetosphere are known to be generated by drift or drift bounce resonance with energetic ring current particles, and these waves may play a role in modulating the energetic particles in the inner magnetosphere. When examining the magnetic field data collected by the NASA ST-5 satellites in the low Earth orbit, Le et al. [2011] discovered many wave events with frequencies of 30\textendash200 mHz (in the Pc 2\textendash3 band), and they proposed that these wav ...

Chi, P.; Le, G.;

YEAR: 2015     DOI: 10.1002/2015JA021145

drift Alfven ballooning mode; high-m waves; poloidal mode

Release of AE9/AP9/SPM Radiation Belt and Space Plasma Model Version 1.20.002

Johnston, Wm.; O\textquoterightBrien, Paul; Ginet, Gregory;

YEAR: 2015     DOI: 10.1002/2015SW001212

Simultaneous Pi2 observations by the Van Allen Probes inside and outside the plasmasphere

Plasmaspheric virtual resonance (PVR) model has been proposed as one of source mechanisms for low-latitude Pi2 pulsations. Since PVR-associated Pi2 pulsations are not localized inside the plasmasphere, simultaneous multipoint observations inside and outside the plasmasphere require to test the PVR model. Until now, however, there are few studies using simultaneous multisatellite observations inside and outside the plasmasphere for understanding the radial structure of Pi2 pulsation. In this study, we focus on the Pi2 event o ...

Ghamry, E.; Kim, K.-H.; Kwon, H.-J.; Lee, D.-H.; Park, J.-S.; Choi, J.; Hyun, K.; Kurth, W.; Kletzing, C.; Wygant, J.;

YEAR: 2015     DOI: 10.1002/2015JA021095

Pi2; plasmasphere; Plasmaspheric virtual resonance; Van Allen Probes

Statistical characteristic of EMIC waves: Van Allen Probe observations

Utilizing the data from the magnetometer instrument which is a part of the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument suite onboard the Van Allen Probe A from Sep. 2012 to Apr. 2014, when the apogee of the satellite has passed all the MLT sectors, we obtain the statistical distribution characteristic of EMIC waves in the inner magnetosphere over all local times from L=3 to L=6. Compared with the previous statistical results about EMIC waves, the occurrence rates of EMIC waves dis ...

Wang, Dedong; Yuan, Zhigang; Yu, Xiongdong; Deng, Xiaohua; Zhou, Meng; Huang, Shiyong; Li, Haimeng; Wang, Zhenzhen; Qiao, Zheng; Kletzing, C.; Wygant, J.;

YEAR: 2015     DOI: 10.1002/2015JA021089

distribution; EMIC waves; plasmasphere; Van Allen Probes

Statistical properties of plasmaspheric hiss derived from Van Allen Probes data and their Effects on radiation belt electron dynamics

Plasmaspheric hiss is known to play an important role in controlling the overall structure and dynamics of radiation belt electrons inside the plasmasphere. Using newly available Van Allen Probes wave data, which provide excellent coverage in the entire inner magnetosphere, we evaluate the global distribution of the hiss wave frequency spectrum and wave intensity for different levels of substorm activity. Our statistical results show that observed hiss peak frequencies are generally lower than the commonly adopted value (~55 ...

Li, W.; Ma, Q.; Thorne, R.; Bortnik, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Nishimura, Y.;

YEAR: 2015     DOI: 10.1002/2015JA021048

hiss diffusion coefficient; hiss frequency spectrum; Plasmaspheric Hiss; Van Allen Probes

Storm-time occurrence and Spatial distribution of Pc4 poloidal ULF waves in the inner magnetosphere: A Van Allen Probes Statistical study

Poloidal ULF waves are capable of efficiently interacting with energetic particles in the ring current and the radiation belt. Using Van Allen Probes (RBSP) data from October 2012 to July 2014, we investigate the spatial distribution and storm-time occurrence of Pc4 (7-25 mHz) poloidal waves in the inner magnetosphere. Pc4 poloidal waves are sorted into two categories: waves with and without significant magnetic compressional components. Two types of poloidal waves have comparable occurrence rates, both of which are much hig ...

Dai, Lei; Takahashi, Kazue; Lysak, Robert; Wang, Chi; Wygant, John; Kletzing, Craig; Bonnell, John; Cattell, Cynthia; Smith, Charles; MacDowall, Robert; Thaller, Scott; Breneman, Aaron; Tang, Xiangwei; Tao, Xin; Chen, Lunjin;

YEAR: 2015     DOI: 10.1002/2015JA021134

Geomagnetic storm; Pc4 ULF waves; poloidal waves; ring current; solar wind dynamic pressure; Van Allen Probes

A Summary of the BARREL Campaigns: Technique for studying electron precipitation

The Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) studies the loss of energetic electrons from Earth\textquoterights radiation belts. BARREL\textquoterights array of slowly drifting balloon payloads was designed to capitalize on magnetic conjunctions with NASA\textquoterights Van Allen Probes. Two campaigns were conducted from Antarctica in 2013 and 2014. During the first campaign in January and February of 2013, there were three moderate geomagnetic storms with Sym-Hmin < -40 nT. Similarly, two mino ...

Woodger, L.; Halford, A.; Millan, R.; McCarthy, M.; Smith, D.; Bowers, G.; Sample, J.; Anderson, B.; Liang, X.;

YEAR: 2015     DOI: 10.1002/2014JA020874

electron precipitation; event timing; gamma ray burst; multi-point observation; Radiation belts; Van Allen Probes; x-ray spectroscopy

Van Allen Probes investigation of the large scale duskward electric field and its role in ring current formation and plasmasphere erosion in the June 1, 2013 storm

Using the Van Allen Probes we investigate the enhancement in the large scale duskward convection electric field during the geomagnetic storm (Dst ~ -120 nT) on June 1, 2013 and its role in ring current ion transport and energization, and plasmasphere erosion. During this storm, enhancements of ~1-2 mV/m in the duskward electric field in the co-rotating frame are observed down to L shells as low as ~2.3. A simple model consisting of a dipole magnetic field and constant, azimuthally westward, electric field is used to calculat ...

Thaller, S.; Wygant, J.; Dai, L.; Breneman, A.W.; Kersten, K.; Cattell, C.A.; Bonnell, J.W.; Fennell, J.F.; Gkioulidou, Matina; Kletzing, C.A.; De Pascuale, S.; Hospodarsky, G.B.; Bounds, S.;

YEAR: 2015     DOI: 10.1002/2014JA020875

electric field; inner magnetosphere; plasma convection; plasmasphere; ring current; Van Allen Probes

Variability of the pitch angle distribution of radiation belt ultra-relativistic electrons during and following intense geomagnetic storms: Van Allen Probes observations

Fifteen months of pitch angle resolved Van Allen Probes REPT measurements of differential electron flux are analyzed to investigate the characteristic variability of the pitch angle distribution (PAD) of radiation belt ultra-relativistic (>2 MeV) electrons during storm conditions and during the long-term post-storm decay. By modeling the ultra-relativistic electron pitch angle distribution as sinn α, where α is the equatorial pitch angle, we examine the spatio-temporal variations of the n-value. The results show that in ge ...

Ni, Binbin; Zou, Zhengyang; Gu, Xudong; Zhou, Chen; Thorne, Richard; Bortnik, Jacob; Shi, Run; Zhao, Zhengyu; Baker, Daniel; Kanekal, Shrikhanth; Spence, Harlan; Reeves, Geoffrey; Li, Xinlin;

YEAR: 2015     DOI: 10.1002/2015JA021065

adiation belt ultra-relativistic electrons; decay timescales; Geomagnetic storms; Pitch angle distribution; resonant wave-particle interactions; Van Allen Probes

Wave energy budget analysis in the Earth\textquoterights radiation belts uncovers a missing energy

Whistler-mode emissions are important electromagnetic waves pervasive in the Earth\textquoterights magnetosphere, where they continuously remove or energize electrons trapped by the geomagnetic field, controlling radiation hazards to satellites and astronauts and the upper-atmosphere ionization or chemical composition. Here, we report an analysis of 10-year Cluster data, statistically evaluating the full wave energy budget in the Earth\textquoterights magnetosphere, revealing that a significant fraction of the energy corresp ...

Artemyev, A.V.; Agapitov, O.V.; Mourenas, D.; Krasnoselskikh, V.V.; Mozer, F.S.;

YEAR: 2015     DOI: 10.1038/ncomms8143

Astronomy; Fluids and plasma physics; Physical sciences; Planetary sciences

Wave-driven butterfly distribution of Van Allen belt relativistic electrons

Van Allen radiation belts consist of relativistic electrons trapped by Earth\textquoterights magnetic field. Trapped electrons often drift azimuthally around Earth and display a butterfly pitch angle distribution of a minimum at 90\textdegree further out than geostationary orbit. This is usually attributed to drift shell splitting resulting from day\textendashnight asymmetry in Earth\textquoterights magnetic field. However, direct observation of a butterfly distribution well inside of geostationary orbit and the origin of th ...

Xiao, Fuliang; Yang, Chang; Su, Zhenpeng; Zhou, Qinghua; He, Zhaoguo; He, Yihua; Baker, D.; Spence, H.; Funsten, H.; Blake, J.;

YEAR: 2015     DOI: 10.1038/ncomms9590

Van Allen Probes

Acceleration of ions by electric field pulses in the inner magnetosphere

Intense (~5-15 mV/m), short-lived (<=1 min) electric field pulses have been observed to accompany earthward-propagating, dipolarizing flux bundles (DFB; flux tubes with a strong magnetic field) before they are stopped by the strong dipole field. Using Time History of Events and Macroscale Interactions During Substorms (THEMIS) observations and test particle modeling, we investigate particle acceleration around L-shell ~7-9 in the nightside magnetosphere and demonstrate that such pulses can effectively accelerate ions with te ...

Artemyev, A.V.; Liu, J.; Angelopoulos, V.; Runov, A.;

YEAR: 2015     DOI: 10.1002/2015JA021160

injections; inner magnetosphere; ion acceleration

Azimuthal flow bursts in the Inner Plasma Sheet and Possible Connection with SAPS and Plasma Sheet Earthward Flow Bursts

We have combined radar observations and auroral images obtained during the PFISR Ion Neutral Observations in the Thermosphere campaign to show the common occurrence of westward moving, localized auroral brightenings near the auroral equatorward boundary and to show their association with azimuthally moving flow bursts near or within the SAPS region. These results indicate that the SAPS region, rather than consisting of relatively stable proton precipitation and westward flows, can have rapidly varying flows, with speeds vary ...

Lyons, L.; Nishimura, Y.; Gallardo-Lacourt, B.; Nicolls, M.; Chen, S.; Hampton, D.; Bristow, W.; Ruohoniemi, J.; Nishitani, N.; Donovan, E.; Angelopoulos, V.;

YEAR: 2015     DOI: 10.1002/2015JA021023

aurora; convection; Flow bursts; plasma sheet; SAPS; streamers

Butterfly pitch-angle distribution of relativistic electrons in the outer radiation belt: Evidence of nonadiabatic scattering

In this paper we investigate the scattering of relativistic electrons in the night-side outer radiation belt (around the geostationary orbit). We consider the particular case of low geomagnetic activity (|Dst|< 20 nT), quiet conditions in the solar wind, and absence of whistler wave emissions. For such conditions we find several events of Van-Allen probe observations of butterfly pitch-angle distributions of relativistic electrons (energies about 1-3 MeV). Many previous publications have described such pitch-angle distributi ...

Artemyev, A.; Agapitov, O.; Mozer, F.; Spence, H.;

YEAR: 2015     DOI: 10.1002/2014JA020865

butterfly distribution; Electron scattering; nonadiabatic dynamics; Radiation belts; Van Allen Probes

Comprehensive analysis of the flux dropout during 7-8 November 2008 storm using multi-satellites observations and RBE model

We investigate an electron flux dropout during a weak storm on 7\textendash8 November 2008, with Dst minimum value being -37 nT. During this period, two clear dropouts were observed on GOES 11 > 2 MeV electrons. We also find a simultaneous dropout in the subrelativistic electrons recorded by Time History of Events and Macroscale Interactions during Substorms probes in the outer radiation belt. Using the Radiation Belt Environment model, we try to reproduce the observed dropout features in both relativistic and subrelativisti ...

Hwang, J.; Choi, E.-J.; Park, J.-S.; Fok, M.-C.; Lee, D.-Y.; Kim, K.-C.; Shin, D.-K.; Usanova, M.; Reeves, G.;

YEAR: 2015     DOI: 10.1002/2015JA021085

atmospheric precipitation; flux dropout; Geomagnetic storm; magneopause shadowing; Radiation belt; RBE model

Direct observations of the full Dungey convection cycle in the polar ionosphere for southward interplanetary magnetic field conditions

Tracking the formation and full evolution of polar cap ionization patches in the polar ionosphere, we directly observe the full Dungey convection cycle for southward interplanetary magnetic field (IMF) conditions. This enables us to study how the Dungey cycle influences the patches\textquoteright evolution. The patches were initially segmented from the dayside storm enhanced density plume (SED) at the equatorward edge of the cusp, by the expansion and contraction of the polar cap boundary (PCB) due to pulsed dayside magnetop ...

Zhang, Q.; Lockwood, M.; Foster, J.; Zhang, S.; Zhang, B.; McCrea, I.; Moen, J.; Lester, M.; Ruohoniemi, Michael;

YEAR: 2015     DOI: 10.1002/2015JA021172

Dungey convection cycle; EISCAT radar; GPS TEC; polar cap patches

Electric field structures and waves at plasma boundaries in the inner magnetosphere

Recent observations by the Van Allen Probes spacecraft have demonstrated that a variety of electric field structures and nonlinear waves frequently occur in the inner terrestrial magnetosphere, including phase space holes, kinetic field line resonances, nonlinear whistler mode waves, and several types of double layer. However, it is unclear whether such structures and waves have a significant impact on the dynamics of the inner magnetosphere, including the radiation belts and ring current. To make progress toward quantifying ...

Malaspina, David; Wygant, John; Ergun, Robert; Reeves, Geoff; Skoug, Ruth; Larsen, Brian;

YEAR: 2015     DOI: 10.1002/2015JA021137

injection; inner magnetosphere; nonlinear electric field structures; plasma boundary; plasma sheet; Van Allen Probes

Equatorial noise emissions with quasiperiodic modulation of wave intensity

Equatorial noise (EN) emissions are electromagnetic wave events at frequencies between the proton cyclotron frequency and the lower hybrid frequency observed in the equatorial region of the inner magnetosphere. They propagate nearly perpendicular to the ambient magnetic field, and they exhibit a harmonic line structure characteristic of the proton cyclotron frequency in the source region. However, they were generally believed to be continuous in time. We investigate more than 2000 EN events observed by the Spatio-Temporal An ...

emec, F.; Santolik, O.; a, Hrb\; Pickett, J.; Cornilleau-Wehrlin, N.;

YEAR: 2015     DOI: 10.1002/2014JA020816

equatorial noise; magnetosonic waves; quasiperiodic modulation

Magnetic field depression within electron holes

We analyze electron holes that are spikes of the electrostatic field (up to 500 mV/m) observed by Van Allen Probes in the outer radiation belt. The unexpected feature is the magnetic field depression of about several tens of picotesla within many of the spikes. The earlier observations showed amplification or negligible perturbations of the magnetic field within the electron holes. We suggest that the observed magnetic field depression is due to the diamagnetic current of hot and highly anisotropic population of electrons tr ...

. Y. Vasko, I; Agapitov, O.; Mozer, F.; Artemyev, A.; Jovanovic, D.;

YEAR: 2015     DOI: 10.1002/2015GL063370

diamagnetic effect; electron hole; outer radiation belt; Van Allen Probes

New model fit functions of the plasmapause location determined using THEMIS observations during the ascending phase of Solar Cycle 24

It is well known that the plasmapause is influenced by the solar wind and magnetospheric conditions. Empirical models of its location have been previously developed such as those by O\textquoterightBrien and Moldwin (2003) and Larsen et al. (2006). In this study, we identified the locations of the plasmapause using the plasma density data obtained from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. We used the data for the period (2008\textendash2012) corresponding to the ascendi ...

Cho, Junghee; Lee, Dae-Young; Kim, Jin-Hee; Shin, Dae-Kyu; Kim, Kyung-Chan; Turner, Drew;

YEAR: 2015     DOI: 10.1002/2015JA021030

Plasmapause; THEMIS

A prediction model for the global distribution of whistler chorus wave amplitude developed separately for two latitudinal zones

Whistler mode chorus waves are considered to play a central role in accelerating and scattering electrons in the outer radiation belt. While in situ measurements are usually limited to the trajectories of a small number of satellites, rigorous theoretical modeling requires a global distribution of chorus wave characteristics. In the present work, by using a large database of chorus wave observations made on the Time History of Events and Macroscale Interactions during Substorms satellites for about 5 years, we develop predic ...

Kim, Jin-Hee; Lee, Dae-Young; Cho, Jung-Hee; Shin, Dae-Kyu; Kim, Kyung-Chan; Li, Wen; Kim, Thomas;

YEAR: 2015     DOI: 10.1002/2014JA020900

Radiation belt; whistler chorus

Role of turbulent transport in the evolution of the κ distribution functions in the plasma sheet

We studied the evolution of ion and electron distribution functions, approximated by κ distributions, in the plasma sheet with the distance from the Earth using the data of the THEMIS spacecraft mission. Five events were used to calculate the main parameters of the κ distribution. For these events at least four spacecraft were aligned along the tail between approximately 7 and 30 Earth radii. It was found that for the majority of events the values of κ increase tailwards. The observed radial profiles could be related to t ...

Stepanova, Marina; Antonova, Elizaveta;

YEAR: 2015     DOI: 10.1002/2014JA020684

Turbolences; plasma-sheet

Solar cycle dependence of ion cyclotron wave frequencies

Electromagnetic ion cyclotron (EMIC) waves have been studied for decades, though remain a fundamentally important topic in heliospheric physics. The connection of EMIC waves to the scattering of energetic particles from Earth\textquoterights radiation belts is one ofmany topics that motivate the need for a deeper understanding of characteristics and occurrence distributions of the waves. In this study, we show that EMIC wave frequencies, as observed at Halley Station in Antarctica from 2008 through 2012, increase by approxim ...

Lessard, Marc; Lindgren, Erik; Engebretson, Mark; Weaver, Carol;

YEAR: 2015     DOI: 10.1002/2014JA020791

EMIC waves; Ion cyclotron; Magnetosphere; plasma waves; Radiation belts; solar cycles

Three-dimensional current systems and ionospheric effects associated with small dipolarisation fronts

We present a case study of eight successive plasma sheet (PS) activations (usually referred to as bursty bulk flows or dipolarization fronts ) associated with small individual inline image increases on 31 March 2009 (0200\textendash0900 UT), observed by the THEMIS mission. This series of events happens during very quiet solar wind conditions, over a period of 7 hours preceding a substorm onset at 1230 UT. The amplitude of the dipolarizations increases with time. The low-amplitude dipolarization fronts are associated with few ...

Palin, L.; Jacquey, C.; Opgenoorth, H.; Connors, M.; Sergeev, V.; Sauvaud, J.-A.; Nakamura, R.; Reeves, G.D.; Singer, H.J.; Angelopoulos, V.; Turc, L.;

YEAR: 2015     DOI: 10.1002/2015JA021040

bursty bulk flow; dipolarization front; field-aligned currents; substorm; substorm current wedge; wedgelet

Time Domain Structures: what and where they are, what they do, and how they are made

Time Domain Structures (TDS) (electrostatic or electromagnetic electron holes, solitary waves, double layers, etc.) are >=1 msec pulses having significant parallel (to the background magnetic field) electric fields. They are abundant through space and occur in packets of hundreds in the outer Van Allen radiation belts where they produce magnetic-field-aligned electron pitch angle distributions at energies up to a hundred keV. TDS can provide the seed electrons that are later accelerated to relativistic energies by whistlers ...

Mozer, F.S.; Agapitov, O.V.; Artemyev, A.; Drake, J.F.; Krasnoselskikh, V.; Lejosne, S.; Vasko, I.;

YEAR: 2015     DOI: 10.1002/2015GL063946

Time Domain Structures; TDS

Unraveling the drivers of the storm time radiation belt response

We present a new framework to study the time evolution and dynamics of the outer Van Allen belt electron fluxes. The framework is entirely based on the large-scale solar wind storm drivers and their substructures. The Van Allen Probe observations, revealing the electron flux behavior throughout the outer belt, are combined with continuous, long-term (over 1.5 solar cycles) geosynchronous orbit data set from GOES and solar wind measurements A superposed epoch analysis, where we normalize the timescales for each substructure ( ...

Kilpua, E.; Hietala, H.; Turner, D.; Koskinen, H.; Pulkkinen, T.; Rodriguez, J.; Reeves, G.; Claudepierre, S.; Spence, H.;

YEAR: 2015     DOI: 10.1002/2015GL063542

coronal mass ejections; Magnetic Storms; Radiation belts; solar wind storm drivers; stream interaction regions; Van Allen Probes

Very Oblique Whistler Generation By Low Energy Electron Streams

Whistler-mode chorus waves are present throughout the Earth\textquoterights outer radiation belt as well as at larger distances from our planet. While the generation mechanisms of parallel lower-band chorus waves and oblique upper-band chorus waves have been identified and checked in various instances, the statistically significant presence in recent satellite observations of very oblique lower-band chorus waves near the resonance cone angle remains to be explained. Here we discuss two possible generation mechanisms for such ...

Mourenas, D.; Artemyev, A.; Agapitov, O.; Krasnoselskikh, V.; Mozer, F.S.;

YEAR: 2015     DOI: 10.1002/2015JA021135

Chorus wave; Cyclotron resonance; Landau resonance; oblique whistler; wave generation

What frequencies of standing surface waves can the subsolar magnetopause support?

It is has been proposed that the subsolar magnetopause may support its own eigenmode, consisting of propagating surface waves which reflect at the northern/southern ionospheres forming a standing wave. While the eigenfrequencies of these so-called Kruskal-Schwartzschild (KS) modes have been estimated under typical conditions, the potential distribution of frequencies over the full range of solar wind conditions is not know. Using models of the magnetosphere and magnetosheath applied to an entire solar cycle\textquoterights w ...

Archer, M.; Plaschke, F.;

YEAR: 2015     DOI: 10.1002/2014JA020545

magnetopause; magnetosheath; Magnetosphere; Ulf; waves

Analysis of plasmaspheric hiss wave amplitudes inferred from low-altitude POES electron data: Technique sensitivity analysis

A novel technique capable of inferring wave amplitudes from low-altitude electron measurements from the POES spacecraft has been previously proposed to construct a global dynamic model of chorus and plasmaspheric hiss waves. In this paper we focus on plasmaspheric hiss, which is an incoherent broadband emission that plays a dominant role in the loss of energetic electrons from the inner magnetosphere. We analyze the sensitivity of the POES technique to different inputs used to infer the hiss wave amplitudes during three conj ...

de Soria-Santacruz, M.; Li, W.; Thorne, R.; Ma, Q.; Bortnik, J.; Ni, B.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.D.; Blake, J.; Fennell, J.;

YEAR: 2015     DOI: 10.1002/2014JA020941

Plasmaspheric Hiss; POES technique; Van Allen Probes; Waves global model

Bounce- and MLT-averaged diffusion coefficients in a physics-based magnetic field geometry obtained from RAM-SCB for the 17 March 2013 storm

Local acceleration via whistler wave and particle interaction plays a significant role in particle dynamics in the radiation belt. In this work we explore gyroresonant wave-particle interaction and quasi-linear diffusion in different magnetic field configurations related to the 17 March 2013 storm. We consider the Earth\textquoterights magnetic dipole field as a reference and compare the results against nondipole field configurations corresponding to quiet and stormy conditions. The latter are obtained with the ring current- ...

Zhao, Lei; Yu, Yiqun; Delzanno, Gian; Jordanova, Vania;

YEAR: 2015     DOI: 10.1002/2014JA020858

diffusion coefficients; Radiation belt; ring current

A computational and theoretical investigation of nonlinear wave-particle interactions in oblique whistlers

Most previous work on nonlinear wave-particle interactions between energetic electrons and VLF waves in the Earth\textquoterights magnetosphere has assumed parallel propagation, the underlying mechanism being nonlinear trapping of cyclotron resonant electrons in a parabolic magnetic field inhomogeneity. Here nonlinear wave-particle interaction in oblique whistlers in the Earth\textquoterights magnetosphere is investigated. The study is nonself-consistent and assumes an arbitrarily chosen wave field. We employ a \textquotedbl ...

Nunn, David; Omura, Yoshiharu;

YEAR: 2015     DOI: 10.1002/2014JA020898

Chorus; nonlinear process; oblique propagation; simulation; Wave-particle interaction; whistler



  10      11      12      13      14      15