Biblio

Found 830 results
2016
Authors: Ma Q, Li W, Thorne R M, Nishimura Y., Zhang X.-J., et al.
Title: Simulation of energy-dependent electron diffusion processes in the Earth's outer radiation belt
Abstract: The radial and local diffusion processes induced by various plasma waves govern the highly energetic electron dynamics in the Earth's radiation belts, causing distinct characteristics in electron distributions at various energies. In this study, we present our simulation results of the energetic electron evolution during a geomagnetic storm using the University of California, Los Angeles 3-D diffusion code. Following the plasma sheet electron injections, the electrons at different energy bands detected by the Magnetic Electron Ion Spectrometer (MagEIS) and Relativistic Electron Proton Telescope (REPT) instruments on board the Van Allen Probes exhibit a rapid enhancement followed by a slow diffusive movement in differential energy fluxes, and the radial extent to which electrons can penetra. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022507 Available at: http://doi.wiley.com/10.1002/2016JA022507
More Details
Authors: Sarno-Smith Lois K., Larsen Brian A., Skoug Ruth M., Liemohn Michael W., Breneman Aaron, et al.
Title: Spacecraft surface charging within geosynchronous orbit observed by the Van Allen Probes
Abstract: Using the Helium Oxygen Proton Electron (HOPE) and Electric Field and Waves (EFW) instruments from the Van Allen Probes, we explored the relationship between electron energy fluxes in the eV and keV ranges and spacecraft surface charging. We present statistical results on spacecraft charging within geosynchronous orbit by L and MLT. An algorithm to extract the H+ charging line in the HOPE instrument data was developed to better explore intense charging events. Also, this study explored how spacecraft potential relates to electron number density, electron pressure, electron temperature, thermal electron current, and low-energy ion density between 1 and 210 eV. It is demonstrated that it is imperative to use both EFW potential measurements and the HOPE instrument ion charging line for examin. . .
Date: 02/2016 Publisher: Space Weather Pages: n/a - n/a DOI: 10.1002/2015SW001345 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015SW001345/full
More Details
Authors: Zhang X.-J., Li W, Thorne R M, Angelopoulos V, Bortnik J, et al.
Title: Statistical distribution of EMIC wave spectra: Observations from Van Allen Probes
Abstract: 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 show that as the ratio of plasma frequency over electron gyrofrequency increases, EMIC wave power becomes progressively dominated by the helium band. There is a pronounced dawn-dusk asymmetry in the wave amplitude and the frequency spectrum. The frequency spectrum does n. . .
Date: 12/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL071158 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071158/full
More Details
Authors: Boyd A.J., Spence H.E., Huang C.-L., Reeves G D, Baker D N, et al.
Title: Statistical Properties of the Radiation Belt Seed Population
Abstract: We present a statistical analysis of phase space density data from the first 26 months of the Van Allen Probes mission. In particular we investigate the relationship between the 10s-100s keV seed electrons and >1 MeV core radiation belt electron population. Using a cross correlation analysis, we find that the seed and core populations are well correlated with a coefficient of ≈ 0.73 with a time lag of 10-15 hours. We present evidence of a seed population threshold that is necessary for subsequent acceleration. The depth of penetration of the seed population determines the inner boundary of the acceleration process. However, we show that an enhanced seed population alone is not enough to produce acceleration in the higher energies, implying that the seed population of 100s of keV electron. . .
Date: 07/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022652 Available at: http://doi.wiley.com/10.1002/2016JA022652
More Details
Authors: Shi Run, Summers Danny, Ni Binbin, Manweiler Jerry W., Mitchell Donald G., et al.
Title: A statistical study of proton pitch angle distributions measured by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE)
Abstract: A statistical study of ring current-energy proton pitch angle distributions (PADs) in Earth's inner magnetosphere is reported here. The data are from the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on board the Van Allen Probe B spacecraft from January 1, 2013 to April 15, 2015. By fitting the data to the functional form sinnα, where α is the proton pitch angle, we examine proton PADs at the energies 50, 100, 180, 328 and 488 keV in the L-shell range from L = 2.5 to L = 6. Three PAD types are classified: trapped (90° peaked), butterfly and isotropic. The proton PAD dependence on the particle energy, MLT, L-shell, and geomagnetic activity are analyzed in detail. The results show a strong dependence of the proton PADs on MLT. On the nightside, the n values o. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA022140 Available at: http://doi.wiley.com/10.1002/2015JA022140
More Details
Authors: Zheng Hao, Holzworth Robert H., Brundell James B., Jacobson Abram R., Wygant John R., et al.
Title: A Statistical Study of Whistler Waves Observed by Van Allen Probes (RBSP) and Lightning Detected by WWLLN
Abstract: Lightning-generated whistler waves are electromagnetic plasma waves in the very low frequency (VLF) band, which play an important role in the dynamics of radiation belt particles. In this paper, we statistically analyze simultaneous waveform data from the Van Allen Probes (Radiation Belt Storm Probes, RBSP) and global lightning data from the World Wide Lightning Location Network (WWLLN). Data were obtained between July to September 2013 and between March and April 2014. For each day during these periods, we predicted the most probable 10 min for which each of the two RBSP satellites would be magnetically conjugate to lightning producing regions. The prediction method uses integrated WWLLN stroke data for that day obtained during the three previous years. Using these predicted times for mag. . .
Date: 03/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA022010 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA022010/full
More Details
Authors: Keika Kunihiro, Seki Kanako, é Masahito, Machida Shinobu, Miyoshi Yoshizumi, et al.
Title: Storm time impulsive enhancements of energetic oxygen due to adiabatic acceleration of preexisting warm oxygen in the inner magnetosphere
Abstract: 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 22–23 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 evolution of the proton and oxygen energy spectra at L ~ 6 during the injection event. The spectral slope did not significantly change during the storm. The oxygen phase space density (PSD) was shifted toward higher PSD in a wide range of the first adiabatic invariant. . .
Date: 08/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: 7739 - 7752 DOI: 10.1002/2016JA022384 Available at: http://doi.wiley.com/10.1002/2016JA022384
More Details
Authors: Gkioulidou Matina, Ukhorskiy A., Mitchell D G, and Lanzerotti L J
Title: Storm-time dynamics of ring current protons: Implications for the long-term energy budget in the inner magnetosphere
Abstract: Our investigation of the long-term ring current proton pressure evolution in Earth's inner magnetosphere based on Van Allen Probes data shows drastically different behavior of the low- and high- energy components of the ring current proton population with respect to the Sym-H index variation. We found that while the low-energy component of the protons (<80 keV) is strongly governed by convective timescales and is very well correlated with the absolute value of Sym-H index, the high-energy component (>100 keV) varies on much longer timescales and shows either no or anti-correlation with the absolute value of Sym-H index. Our study also shows that the contributions of the low- and high- energy protons to the inner magnetosphere energy content are comparable. Thus, our results conclusivel. . .
Date: 03/2016 Publisher: Geophysical Research Letters Pages: n/a - n/a DOI: 10.1002/2016GL068013 Available at: http://doi.wiley.com/10.1002/2016GL068013http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2016GL068013
More Details
Authors: Gkioulidou Matina, Ukhorskiy A., Mitchell D G, and Lanzerotti L J
Title: Storm-time dynamics of ring current protons: Implications for the long-term energy budget in the inner magnetosphere
Abstract: Our investigation of the long-term ring current proton pressure evolution in Earth's inner magnetosphere based on Van Allen Probes data shows drastically different behavior of the low- and high- energy components of the ring current proton population with respect to theSYM-H index variation. We found that while the low-energy component of the protons (<80 keV) is strongly governed by convective timescales and is very well correlated with the absolute value of SYM-H index, the high-energy component (>100 keV) varies on much longer timescales and shows either no correlation or anticorrelation with the absolute value of SYM-H index. Our study also shows that the contributions of the low- and high- energy protons to the inner magnetosphere energy content are comparable. Thus, our results c. . .
Date: 05/2016 Publisher: Geophysical Research Letters Pages: n/a - n/a DOI: 10.1002/2016GL068013 Available at: http://doi.wiley.com/10.1002/2016GL068013
More Details
Authors: Liu Y., Zong Q.-G., Zhou X.-Z., Foster J. C., and Rankin R
Title: Structure and Evolution of Electron "Zebra Stripes" in the Inner Radiation Belt
Abstract: Zebra stripes” are newly found energetic electron energy-spatial (L shell) distributed structure with an energy between tens to a few hundreds keV in the inner radiation belt. Using high-quality measurements of electron fluxes from Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) on board the twin Van Allen Probes, we carry out case and statistical studies from April 2013 to April 2014 to study the structural and evolutionary characteristics of zebra stripes below L = 3. It is revealed that the zebra stripes can be transformed into evenly spaced patterns in the electron drift frequency coordinate: the detrended logarithmic fluxes in each L shell region can be well described by sinusoidal functions of drift frequency. The “wave number” of this sinusoidal function, whic. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA022077 Available at: http://doi.wiley.com/10.1002/2015JA022077
More Details
Authors: Boardsen Scott A, Hospodarsky George B, Kletzing Craig, Engebretson Mark, Pfaff Robert F, et al.
Title: Survey of the Frequency Dependent Latitudinal Distribution of the Fast Magnetosonic Wave Mode from Van Allen Probes EMFISIS Wave Form Receiver Plasma Wave Analysis
Abstract: We present a statistical survey of the latitudinal structure of the fast magnetosonic wave mode detected by the Van Allen Probes spanning the time interval of 9/21/2012 to 8/1/2014. We show that statistically the latitudinal occurrence of the wave frequency (f) normalized by the local proton cyclotron frequency (fcP) has a distinct funnel shaped appearance in latitude about the magnetic equator similar to that found in case studies. By comparing the observed E/B ratios with the model E/B ratio, using the observed plasma density and background magnetic field magnitude as input to the model E/B ratio, we show that this mode is consistent with the extraordinary (whistler) mode at wave normal angles (θk) near 90°. Performing polarization analysis on synthetic waveforms composed from a superp. . .
Date: 02/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA021844 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA021844/full
More Details
Authors: Baker D N, Jaynes A. N., Turner D. L., Nakamura R, Schmid D., et al.
Title: A telescopic and microscopic examination of acceleration in the June 2015 geomagnetic storm: Magnetospheric Multiscale and Van Allen Probes study of substorm particle injection
Abstract: An active storm period in June 2015 showed that particle injection events seen sequentially by the four (Magnetospheric Multiscale) MMS spacecraft subsequently fed the enhancement of the outer radiation belt observed by Van Allen Probes mission sensors. Several episodes of significant southward interplanetary magnetic field along with a period of high solar wind speed (Vsw ≳ 500 km/s) on 22 June occurred following strong interplanetary shock wave impacts on the magnetosphere. Key events on 22 June 2015 show that the magnetosphere progressed through a sequence of energy-loading and stress-developing states until the entire system suddenly reconfigured at 19:32 UT. Energetic electrons, plasma, and magnetic fields measured by the four MMS spacecraft revealed clear dipolarization front. . .
Date: 06/2016 Publisher: Geophysical Research Letters Pages: 6051 - 6059 DOI: 10.1002/grl.v43.1210.1002/2016GL069643 Available at: http://doi.wiley.com/10.1002/2016GL069643
More Details
Authors: Kessel Mona
Title: Things we don't yet understand about solar driving of the radiation belts.
Abstract: This commentary explores how close we are to predicting the behavior of the radiations belts - the primary science objective of NASA's Van Allen Probes mission. Starting with what we know or think we know about competing sources, enhancement, transport, and loss, I walk through recent papers that have improved our understanding and then focus on flux dropouts as one particular yardstick of success. I mention a new paradigm for electrons and the importance of reliably matching models and observations for different solar inputs. Although the case for prediction remains a work in progress, there are encouraging signs of progress.
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022472 Available at: http://doi.wiley.com/10.1002/2016JA022472
More Details
Authors: Ripoll J. F., Loridan V., Cunningham G. S., Reeves G D, and Shprits Y Y
Title: On the Time Needed to Reach an Equilibrium Structure of the Radiation Belts
Abstract: In this study, we complement the notion of equilibrium states of the radiation belts with a discussion on the dynamics and time needed to reach equilibrium. We solve for the equilibrium states obtained using 1D radial diffusion with recently developed hiss and chorus lifetimes at constant values of Kp = 1, 3 and 6. We find that the equilibrium states at moderately low Kp, when plotted vs L-shell (L) and energy (E), display the same interesting S-shape for the inner edge of the outer belt as recently observed by the Van Allen Probes. The S-shape is also produced as the radiation belts dynamically evolve toward the equilibrium state when initialized to simulate the buildup after a massive dropout or to simulate loss due to outward diffusion from a saturated state. Physically, this shape,. . .
Date: 06/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA022207 Available at: http://doi.wiley.com/10.1002/2015JA022207
More Details
Authors: Yue Chao, Bortnik Jacob, Chen Lunjin, Ma Qianli, Thorne Richard M, et al.
Title: Transitional behavior of different energy protons based on Van Allen Probes observations
Abstract: 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 flux distributions near geomagnetic equator by using Van Allen Probes observations to investigate the H+ dynamics under the regulation of large-scale electric and magnetic fields. Our survey clearly indicates three types of H+ behaviors within different energy ranges, whic. . .
Date: 12/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL071324 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071324/full
More Details
Authors: Lejosne ène, and Mozer F S
Title: Typical values of the electric drift E  ×  B / B 2 in the inner radiation belt and slot region as determined from Van Allen Probe measurements
Abstract: The electric drift E × 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 dependences of the components on radial distance, magnetic local time, and geographic longitude are examined. The results from Van Allen Probe A agree with Van Allen Probe B. They show, among other things, a typical corotation lag of the order of 5 to 10% below L ~ 2.6, as w. . .
Date: 12/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023613 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023613/full
More Details
Authors: Li Jinxing, Bortnik Jacob, Thorne Richard M, Li Wen, Ma Qianli, et al.
Title: Ultrarelativistic electron butterfly distributions created by parallel acceleration due to magnetosonic waves
Abstract: The Van Allen Probe observations during the recovery phase of a large storm that occurred on 17 March 2015 showed that the ultrarelativistic electrons at the inner boundary of the outer radiation belt (L* = 2.6–3.7) exhibited butterfly pitch angle distributions, while the inner belt and the slot region also showed evidence of sub-MeV electron butterfly distributions. Strong magnetosonic waves were observed in the same regions and at the same time periods as these butterfly distributions. Moreover, when these magnetosonic waves extended to higher altitudes (L* = 4.1), the butterfly distributions also extended to the same region. Combining test particle calculations and Fokker-Planck diffusion simulations, we successfully reproduced the formation of the ultrarelativistic electron b. . .
Date: 04/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: 3212 - 3222 DOI: 10.1002/2016JA022370 Available at: http://doi.wiley.com/10.1002/2016JA022370
More Details
Authors: Li W, Mourenas D., Artemyev A. V., Bortnik J, Thorne R M, et al.
Title: Unraveling the excitation mechanisms of highly oblique lower band chorus waves
Abstract: Excitation mechanisms of highly oblique, quasi-electrostatic lower band chorus waves are investigated using Van Allen Probes observations near the equator of the Earth's 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 time. The first mechanism relies on cyclotron resonance with electrons possessing both a realistic temperature anisotropy at keV energies and a plateau at 100–500 eV in the parallel velocity distribution. The second mechanism corresponds to Landau resonance with a 100–500 eV . . .
Date: 09/2016 Publisher: Geophysical Research Letters Pages: 8867 - 8875 DOI: 10.1002/grl.v43.1710.1002/2016GL070386 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL070386/abstract
More Details
Authors: Hartley D. P., Kletzing C A, Kurth W S, Bounds S R, Averkamp T. F., et al.
Title: Using the cold plasma dispersion relation and whistler-mode waves to quantify the antenna sheath impedance of the Van Allen Probes EFW instrument
Abstract: Cold plasma theory and parallel wave propagation are often assumed when approximating the whistler mode magnetic field wave power from electric field observations. The current study is the first to include the wave normal angle from the Electric and Magnetic Field Instrument Suite and Integrated Science package on board the Van Allen Probes in the conversion factor, thus allowing for the accuracy of these assumptions to be quantified. Results indicate that removing the assumption of parallel propagation does not significantly affect calculated plasmaspheric hiss wave powers. Hence, the assumption of parallel propagation is valid. For chorus waves, inclusion of the wave normal angle in the conversion factor leads to significant alterations in the distribution of wave power ratios (observed/. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022501 Available at: http://doi.wiley.com/10.1002/2016JA022501
More Details
Authors: Lejosne Solène, and Mozer F S
Title: Van Allen Probe measurements of the electric drift E × B/B2 at Arecibo's L = 1.4 field line coordinate
Abstract: We have used electric and magnetic measurements by Van Allen Probe B from 2013 to 2014 to examine the equatorial electric drift E × B/B2 at one field line coordinate set to Arecibo's incoherent scatter radar location (L = 1.43). We report on departures from the traditional picture of corotational motion with the Earth in two ways: (1) the rotational angular speed is found to be 10% smaller than the rotational angular speed of the Earth, in agreement with previous works on plasmaspheric notches, and (2) the equatorial electric drift displays a dependence in magnetic local time, with a pattern consistent with the mapping of the Arecibo ionosphere dynamo electric fields along equipotential magnetic field lines. The electric fields due to the ionosphere dynamo are therefore expected t. . .
Date: 07/2016 Publisher: Geophysical Research Letters Pages: 6768 - 6774 DOI: 10.1002/2016GL069875 Available at: http://doi.wiley.com/10.1002/2016GL069875
More Details
Authors: Maurer R H, and Goldsten J O
Title: The Van Allen Probes Engineering Radiation Monitor: Mission Radiation Environment and Effects
Abstract: The engineering radiation monitor (ERM) measures dose, dose rate, and charging currents on the Van Allen Probes mission to study the dynamics of Earth’s Van Allen radiation belts. Measurements from this monitor show a variation in dose rates with time, a correlation between the dosimeter and charging current data, a map of charging current versus orbit altitude, and a comparison of measured cumulative dose to prelaunch and postlaunch modeling. The measurement results and surveys of the radiation hardness for the spacecraft and science instrument electronics enable the team to predict the length of possible mission extensions. The ERM data have proved useful in investigations of two spacecraft anomalies.
Date: 07/2016 Publisher: Johns Hopkins APL Technical Digest Pages: 183-193 DOI: N/A Available at: http://www.jhuapl.edu/techdigest/TD/td3303/33_03-Maurer.pdf
More Details
Authors: Chen X.-R., Zong Q.-G., Zhou X.-Z., Blake Bernard, Wygant John R., et al.
Title: Van Allen Probes observation of a 360° phase shift in the flux modulation of injected electrons by ULF waves
Abstract: 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°. This phase relationship is different from the characteristic 180° phase shift as expected from the drift-resonance theory. We speculate that the additional 180° phase difference arises from the inversion of electron phase space density (PSD) gradient, which in turn is caused by the drift motion of the substorm injected electrons. This PSD gradient adjusts the characteristic . . .
Date: 12/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL071252 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071252/full
More Details
Authors: Colpitts C. A., Cattell C. A., Engebretson M., Broughton M., Tian S., et al.
Title: Van Allen Probes observations of cross-scale coupling between electromagnetic ion cyclotron waves and higher-frequency wave modes
Abstract: We present observations of higher-frequency (~50–2500 Hz, ~0.1–0.7 fce) wave modes modulated at the frequency of colocated lower frequency (0.5–2 Hz, on the order of fci) waves. These observations come from the Van Allen Probes Electric Field and Waves instrument's 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 a few tens of seconds but are in some cases observed repeatedly over several hours. The higher-frequency waves are observed to be unmodulated before and after the presence of the electromagnetic ion cyclotron (EMIC) waves, but when the EMIC waves are present, the amplitude of the higher-frequency waves . . .
Date: 11/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL071566 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071566/full
More Details
Authors: Cho J.-H., Lee D.-Y., Noh S.-J., Shin D.-K., Hwang J., et al.
Title: Van Allen Probes Observations of Electromagnetic Ion Cyclotron Waves Triggered by Enhanced Solar Wind Dynamic Pressure
Abstract: 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 plasmapause at post-midnight and near the equator (magnetic latitude (MLAT) ~ -3o). Event 2 occurs by a sharp Pdyn pulse impact while Van Allen Probe-A is located inside the plasmapause in the dawn sector and rather away from the equator (MLAT ~ 12o). Event 3 is c. . .
Date: 09/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022841 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA022841/full
More Details
Authors: é M., Keika K, Kletzing C A, Spence H E, Smith C W, et al.
Title: Van Allen Probes observations of magnetic field dipolarization and its associated O + flux variations in the inner magnetosphere at L  < 6.6
Abstract: We investigate magnetic field dipolarization in the inner magnetosphere and its associated ion flux variations, using the magnetic field and energetic ion flux data acquired by the Van Allen Probes. From a study of 74 events that appeared at L = 4.5–6.6 between 1 October 2012 and 31 October 2013, we reveal the following characteristics of the dipolarization in the inner magnetosphere: (1) its timescale is approximately 5 min, (2) it is accompanied by strong magnetic fluctuations that have a dominant frequency close to the O+ gyrofrequency, (3) ion fluxes at 20–50 keV are simultaneously enhanced with larger magnitudes for O+ than for H+, (4) after a few minutes of the dipolarization, the flux enhancement at 0.1–5 keV appears with a clear energy-dispersion signature only for . . .
Date: 07/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022549 Available at: http://doi.wiley.com/10.1002/2016JA022549
More Details
Authors: Usanova M. E., Malaspina D. M., Jaynes A. N., Bruder R. J., Mann I. R., et al.
Title: Van Allen Probes observations of oxygen cyclotron harmonic waves in the inner magnetosphere
Abstract: 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 the wave velocity and the Poynting vector directed almost parallel to the background magnetic field. These properties are very similar to those of electromagnetic ion cyclotron waves, which are believed to contribute to loss of ring current ions and radiation belt electro. . .
Date: 09/2016 Publisher: Geophysical Research Letters Pages: 8827 - 8834 DOI: 10.1002/grl.v43.1710.1002/2016GL070233 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL070233/abstract
More Details
Authors: Foster J. C., Erickson P. J., Omura Y., Baker D N, Kletzing C A, et al.
Title: Van Allen Probes Observations of Prompt MeV Radiation Belt Electron Acceleration in Non-Linear Interactions with VLF Chorus
Abstract: 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 Van Allen Probes, we investigate the efficiency of non-linear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy 100s keV - 3 MeV can be accelerated by 50 keV - 200 keV in re. . .
Date: 12/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023429 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023429/full
More Details
Authors: Sigsbee K., Kletzing C A, Smith C W, MacDowall Robert, Spence Harlan, et al.
Title: Van Allen Probes, THEMIS, GOES, and Cluster Observations of EMIC waves, ULF pulsations, and an electron flux dropout
Abstract: We examined an electron flux dropout during the 12–14 November 2012 geomagnetic storm using observations from seven spacecraft: the two Van Allen Probes, THEMIS-A (P5), Cluster 2, and Geostationary Operational Environmental Satellite (GOES) 13, 14, and 15. The electron fluxes for energies greater than 2.0 MeV observed by GOES 13, 14, and 15 at geosynchronous orbit and by the Van Allen Probes remained at or near instrumental background levels for more than 24 hours from 12–14 November. For energies of 0.8 MeV, the GOES satellites observed two shorter intervals of reduced electron fluxes. The first interval of reduced 0.8 MeV electron fluxes on 12–13 November was associated with an interplanetary shock and a sudden impulse. Cluster, THEMIS, and GOES observed intense He+ EMIC wa. . .
Date: 01/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020877 Available at: http://doi.wiley.com/10.1002/2014JA020877
More Details
Authors: Matsuda Shoya, Kasahara Yoshiya, and Kletzing Craig A.
Title: Variation in crossover frequency of EMIC waves in plasmasphere estimated from ion cyclotron whistler waves observed by Van Allen Probe A
Abstract: We report variations in the propagation of the H+ band ion cyclotron whistlers observed by Van Allen Probe A. Ion cyclotron whistlers are one of the EMIC (electromagnetic ion cyclotron) waves generated by mode conversion from lightning whistlers. Crossover frequency is an important frequency for the ion cyclotron whistlers, which is a function of the variations in the local heavy-ion composition. We surveyed waveform data obtained by the Electric and Magnetic Field Instrument and Integrated Science instrument and found that 3461 H+ band ion cyclotron whistlers were observed from 572 km to 5992 km in altitude. The main finding is that the crossover frequencies of the observed events decreased with increasing altitude. These results support the hypothesis that the total heavy-ion density dec. . .
Date: 01/2016 Publisher: Geophysical Research Letters Pages: 28 - 34 DOI: 10.1002/2015GL066893 Available at: http://doi.wiley.com/10.1002/2015GL066893
More Details
Authors: Nakayama Y., Ebihara Y., Ohtani S, Gkioulidou M., Takahashi K., et al.
Title: Void structure of O + ions in the inner magnetosphere observed by the Van Allen Probes
Abstract: 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 the void structure. The structure cannot be found in the H+ spectrogram. We studied the generation mechanism of this structure by using numerical simulation. We traced the trajectories of O+ ions in the electric and magnetic fields from the global magnetohydrodynamic. . .
Date: 11/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023013 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023013/full
More Details
Authors: He Zhaoguo, Yan Qi, Chu Yuchuan, and Cao Yong
Title: Wave-driven gradual loss of energetic electrons in the slot region
Abstract: 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 100–600 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 energetic electrons within 2 days. Our quasi-linear diffusion simulations show that hiss scattering can basically reproduce the temporal evolution of the angular distribution of the observed electron flux decay. This quantitative analysis provides further support for the mechan. . .
Date: 09/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023087 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2016JA023087/full
More Details
Authors: Forsyth C., Rae I. J., Murphy K. R., Freeman M. P., Huang C.-L., et al.
Title: What effect do substorms have on the content of the radiation belts?
Abstract: Substorms are fundamental and dynamic processes in the magnetosphere, converting captured solar wind magnetic energy into plasma energy. These substorms have been suggested to be a key driver of energetic electron enhancements in the outer radiation belts. Substorms inject a keV “seed” population into the inner magnetosphere which is subsequently energized through wave-particle interactions up to relativistic energies; however, the extent to which substorms enhance the radiation belts, either directly or indirectly, has never before been quantified. In this study, we examine increases and decreases in the total radiation belt electron content (TRBEC) following substorms and geomagnetically quiet intervals. Our results show that the radiation belts are inherently lossy, shown by a negat. . .
Date: 06/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022620 Available at: http://doi.wiley.com/10.1002/2016JA022620
More Details
Authors: Lejosne Solène, and Roederer Juan G.
Title: The “zebra stripes”: An effect of F-region zonal plasma drifts on the longitudinal distribution of radiation belt particles
Abstract: We examine a characteristic effect, namely, the ubiquitous appearance of structured peaks and valleys called zebra stripes in the spectrograms of energetic electrons and ions trapped in the inner belt below L ~ 3. We propose an explanation of this phenomenon as a purely kinematic consequence of particle drift velocity modulation caused by F region zonal plasma drifts in the ionosphere. In other words, we amend the traditional assumption that the electric field associated with ionospheric plasma drives trapped particle distributions into rigid corotation with the Earth. An equation based on a simple first-order model is set up to determine quantitatively the appearance of zebra stripes as a function of magnetic time. Our numerical predictions are in agreement with measurements by the Ra. . .
Date: 01/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021925 Available at: http://doi.wiley.com/10.1002/2015JA021925
More Details
2015
Authors: Li Zhao, Hudson Mary, Kress Brian, and Paral Jan
Title: 3D test-particle simulation of the 17-18 March, 2013 CME-shock driven storm
Abstract: 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 after a strong CME-shock arrival which produced a Dst=−132 nT storm, and recovery to the pre-storm value later, consistent with GOES satellite measurements. This study provides the first 3D test-particle simulation combining the trapped and injected populations. The r. . .
Date: 06/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL064627 Available at: http://doi.wiley.com/10.1002/2015GL064627
More Details
Authors: Artemyev A.V., Liu J., Angelopoulos V, and Runov A.
Title: Acceleration of ions by electric field pulses in the inner magnetosphere
Abstract: 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 tens of keV initial energy to hundreds of keV. This acceleration occurs because the ion gyroradius is comparable to the spatial scale of the localized electric field pulse at the leading edge of the flux bundle before it stops. The proposed acceleration mechanism can rep. . .
Date: 05/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021160 Available at: http://doi.wiley.com/10.1002/2015JA021160
More Details
Authors: de Soria-Santacruz M., Li W, Thorne R M, Ma Q, Bortnik J, et al.
Title: Analysis of plasmaspheric hiss wave amplitudes inferred from low-altitude POES electron data: Validation with conjunctive Van Allen Probes observations
Abstract: Plasmaspheric hiss plays an important role in controlling the overall structure and dynamics of the Earth's radiation belts. The interaction of plasmaspheric hiss with radiation belt electrons is commonly evaluated using diffusion codes, which rely on statistical models of wave observations that may not accurately reproduce the instantaneous global wave distribution, or the limited in-situ satellite wave measurements from satellites. This paper evaluates the performance and limitations of a novel technique capable of inferring wave amplitudes from low-altitude electron flux observations from the POES spacecraft, which provide extensive coverage in L-shell and MLT. We found that, within its limitations, this technique could potentially be used to build a dynamic global model of the plasmasp. . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021148 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA021148/abstract
More Details
Authors: de Soria-Santacruz M., Li W, Thorne R M, Ma Q, Bortnik J, et al.
Title: Analysis of plasmaspheric hiss wave amplitudes inferred from low-altitude POES electron data: Technique sensitivity analysis
Abstract: 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 conjunction events with the Van Allen Probes. These amplitudes are calculated with different input models of the plasma density, wave frequency spectrum, and electron energy spectrum, and the results are compared to the wave observations from the twin Van Allen Probes. Only. . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020941 Available at: http://doi.wiley.com/10.1002/2014JA020941
More Details
Authors: Simms Laura E., Engebretson Mark J, Smith A. J., Clilverd Mark, Pilipenko Viacheslav, et al.
Title: Analysis of the effectiveness of ground-based VLF wave observations for predicting or nowcasting relativistic electron flux at geostationary orbit
Abstract: Poststorm relativistic electron flux enhancement at geosynchronous orbit has shown correlation with very low frequency (VLF) waves measured by satellite in situ. However, our previous study found little correlation between electron flux and VLF measured by a ground-based instrument at Halley, Antarctica. Here we explore several possible explanations for this low correlation. Using 220 storms (1992–2002), our previous work developed a predictive model of the poststorm flux at geosynchronous orbit based on explanatory variables measured a day or two before the flux increase. In a nowcast model, we use averages of variables from the time period when flux is rising during the recovery phase of geomagnetic storms and limit the VLF (1.0 kHz) measure to the dawn period at Halley (09:00–12:0. . .
Date: 03/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 2052 - 2060 DOI: 10.1002/2014JA020337 Available at: http://doi.wiley.com/10.1002/2014JA020337
More Details
Authors: Hartley D. P., Chen Y., Kletzing C A, Denton M. H., and Kurth W S
Title: Applying the cold plasma dispersion relation to whistler mode chorus waves: EMFISIS wave measurements from the Van Allen Probes
Abstract: Most theoretical wave models require the power in the wave magnetic field in order to determine the effect of chorus waves on radiation belt electrons. However, researchers typically use the cold plasma dispersion relation to approximate the magnetic wave power when only electric field data are available. In this study, the validity of using the cold plasma dispersion relation in this context is tested using Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) observations of both the electric and magnetic spectral intensities in the chorus wave band (0.1–0.9 fce). Results from this study indicate that the calculated wave intensity is least accurate during periods of enhanced wave activity. For observed wave intensities >10−3 nT2, using the cold plasma dispersi. . .
Date: 02/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020808 Available at: http://doi.wiley.com/10.1002/2014JA020808
More Details
Authors: Mourenas D., Artemyev A. V., and Agapitov O.V.
Title: Approximate analytical formulation of radial diffusion and whistler-induced losses from a pre-existing flux peak in the plasmasphere
Abstract: Modeling the spatio-temporal evolution of relativistic electron fluxes trapped in the Earth's radiation belts in the presence of radial diffusion coupled with wave-induced losses should address one important question: how deep can relativistic electrons penetrate into the inner magnetosphere? However, a full modelling requires extensive numerical simulations solving the comprehensive quasi-linear equations describing pitch-angle and radial diffusion of the electron distribution, making it rather difficult to perform parametric studies of the flux behavior. Here, we consider the particular situation where a localized flux peak (or storage ring) has been produced at low L < 4 during a period of strong disturbances, through a combination of chorus-induced energy diffusion (or direct injection. . .
Date: 08/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021623 Available at: http://doi.wiley.com/10.1002/2015JA021623
More Details
Authors: Lyons L R, Nishimura Y., Gallardo-Lacourt B., Nicolls M. J., Chen S., et al.
Title: Azimuthal flow bursts in the Inner Plasma Sheet and Possible Connection with SAPS and Plasma Sheet Earthward Flow Bursts
Abstract: 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 varying from ~100 m/s to ~1 km/s in just a few minutes. The auroral brightenings are associated with bursts of weak electron precipitation that move westward with the westward flow bursts and extend into the SAPS region. Additionally, our observations show evidence that the. . .
Date: 05/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021023 Available at: http://doi.wiley.com/10.1002/2015JA021023
More Details
Authors: Claudepierre S G, O'Brien T P, Blake J B, Fennell J. F., Roeder J. L., et al.
Title: A background correction algorithm for Van Allen Probes MagEIS electron flux measurements
Abstract: 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 MagEIS electron channels (~30-500 keV) and in regions of geospace where multi-MeV electrons are present. Inner zone protons produce contamination in all MagEIS energy channels at roughly L < 2.5. The background corrected MagEIS electron data produce a more accurate me. . .
Date: 06/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021171 Available at: http://doi.wiley.com/10.1002/2015JA021171
More Details
Authors: Halford A J, McGregor S. L., Murphy K. R., Millan R M, Hudson M K, et al.
Title: BARREL observations of an ICME-Shock impact with the magnetosphere and the resultant radiation belt electron loss.
Abstract: The Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) mission of opportunity working in tandem with the Van Allen Probes was designed to study the loss of radiation belt electrons to the ionosphere and upper atmosphere. BARREL is also sensitive to X-rays from other sources. During the second BARREL campaign the Sun produced an X-class flare followed by a solar energetic particle event (SEP) associated with the same active region. Two days later on 9 January 2014 the shock generated by the coronal mass ejection (CME) originating from the active region hit the Earth while BARREL was in a close conjunction with the Van Allen Probes. Time History Events and Macroscale Interactions during Substorms (THEMIS) observed the impact of the ICME-shock near the magnetopause, and th. . .
Date: 03/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020873 Available at: http://doi.wiley.com/10.1002/2014JA020873
More Details
Authors: Over Matthew W., Wollschläger Ute, Osorio-Murillo Carlos Andres, and Rubin Yoram
Title: Bayesian inversion of Mualem-van Genuchten parameters in a multilayer soil profile: A data-driven, assumption-free likelihood function
Abstract: This paper introduces a hierarchical simulation and modeling framework that allows for inference and validation of the likelihood function in Bayesian inversion of vadose zone hydraulic properties. The likelihood function or its analogs (objective functions and likelihood measures) are commonly assumed to be multivariate Gaussian in form; however, this assumption is not possible to verify without a hierarchical simulation and modeling framework. In this paper, we present the necessary statistical mechanisms for utilizing the hierarchical framework. We apply the hierarchical framework to the inversion of the vadose zone hydraulic properties within a multilayer soil profile conditioned on moisture content observations collected in the uppermost four layers. The key result of our work is that. . .
Date: 02/2015 Publisher: Water Resources Research Pages: 861 - 884 DOI: 10.1002/wrcr.v51.210.1002/2014WR015252 Available at: http://doi.wiley.com/10.1002/2014WR015252
More Details
Authors: Zhao Lei, Yu Yiqun, Delzanno Gian Luca, and Jordanova Vania K.
Title: Bounce- and MLT-averaged diffusion coefficients in a physics-based magnetic field geometry obtained from RAM-SCB for the 17 March 2013 storm
Abstract: 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's 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-atmosphere interactions model with a self-consistent magnetic field (RAM-SCB), a code that models the Earth's ring current and provides a realistic modeling of the Earth's magnetic field. By applying quasi-linear theory, the bounce- and Magnetic Local Time (MLT)-averaged electron pit. . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020858 Available at: http://doi.wiley.com/10.1002/2014JA020858
More Details
Authors: Chaston C. C., Bonnell J. W., Kletzing C A, Hospodarsky G B, Wygant J R, et al.
Title: Broadband low frequency electromagnetic waves in the inner magnetosphere
Abstract: A prominent yet largely unrecognized feature of the inner magnetosphere associated with particle injections, and more generally geomagnetic storms, is the occurrence of broadband electromagnetic field fluctuations over spacecraft frame frequencies (fsc) extending from effectively zero to fsc ≳ 100 Hz. Using observations from the Van Allen Probes we show that these waves most commonly occur pre-midnight but are observed over a range of local times extending into the dayside magnetosphere. We find that the variation of magnetic spectral energy density with fsc obeys inline image over several decades with a spectral break-point at fb ≈1 Hz. The values for α are log normally distributed with α = 1.9 ± 0.6 for fsc < fb andα = 2.9 ± 0.6 for fsc > fb. A is . . .
Date: 09/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021690 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015JA021690/abstract
More Details
Authors: Artemyev A. V., Agapitov O. V., Mozer F S, and Spence H.
Title: Butterfly pitch-angle distribution of relativistic electrons in the outer radiation belt: Evidence of nonadiabatic scattering
Abstract: 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 distributions over a wide energy range as due to the combined effect of outward radial diffusion and magnetopause shadowing. In this paper we discuss another mechanism that produces butterfly distributions over a limited range of electron energies. We suggest that such distributi. . .
Date: 05/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020865 Available at: http://doi.wiley.com/10.1002/2014JA020865
More Details
Authors: Shprits Yuri Y, Kellerman Adam, Drozdov Alexander, Spense Harlan, Reeves Geoffrey, et al.
Title: Combined Convective and Diffusive Simulations: VERB-4D Comparison with March 17, 2013 Van Allen Probes Observations
Abstract: This study is focused on understanding the coupling between different electron populations in the inner magnetosphere and the various physical processes that determine evolution of electron fluxes at different energies. Observations during the March 17, 2013 storm and simulations with a newly developed Versatile Electron Radiation Belt-4D (VERB-4D) are presented. Analysis of the drift trajectories of the energetic and relativistic electrons shows that electron trajectories at transitional energies with a first invariant on the scale of ~100MeV/G may resemble ring current or relativistic electron trajectories depending on the level of geomagnetic activity. Simulations with the VERB-4D code including convection, radial diffusion, and energy diffusion are presented. Sensitivity simulations in. . .
Date: 09/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL065230 Available at: http://doi.wiley.com/10.1002/2015GL065230
More Details
Authors: Katsavrias C., Daglis I. A., Li W, Dimitrakoudis S., Georgiou M., et al.
Title: Combined effects of concurrent Pc5 and chorus waves on relativistic electron dynamics
Abstract: We present electron phase space density (PSD) calculations as well as concurrent Pc5 and chorus wave activity observations during two intense geomagnetic storms caused by interplanetary coronal mass ejections (ICMEs) resulting in contradicting net effect. We show that, during the 17 March 2013 storm, the coincident observation of chorus and relativistic electron enhancements suggests that the prolonged chorus wave activity seems to be responsible for the enhancement of the electron population in the outer radiation belt even in the presence of pronounced outward diffusion. On the other hand, the significant depletion of electrons, during the 12 September 2014 storm, coincides with long-lasting outward diffusion driven by the continuous enhanced Pc5 activity since chorus wave a. . .
Date: 09/2015 Publisher: Annales Geophysicae Pages: 1173 - 1181 DOI: 10.5194/angeo-33-1173-2015 Available at: http://www.ann-geophys.net/33/1173/2015/
More Details
Authors: Hwang J., Choi E.-J., Park J.-S., Fok M.-C., Lee D.-Y., et al.
Title: Comprehensive analysis of the flux dropout during 7-8 November 2008 storm using multi-satellites observations and RBE model
Abstract: We investigate an electron flux dropout during a weak storm on 7–8 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 subrelativistic electrons. We found that there are local time dependences in the dropout for both observation and simulation in subrelativistic electrons: (1) particle loss begins from nightside and propagates into dayside and (2) resupply starts from near dawn magnetic local time . . .
Date: 05/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021085 Available at: http://doi.wiley.com/10.1002/2015JA021085
More Details

Pages