Biblio

Found 9 results
Filters: Author is Turner, Drew L.  [Clear All Filters]
2018
Authors: Shumko Mykhaylo, Turner Drew L, O'Brien T P, Claudepierre Seth G., Sample John, et al.
Title: Evidence of Microbursts Observed Near the Equatorial Plane in the Outer Van Allen Radiation Belt
Abstract: We present the first evidence of electron microbursts observed near the equatorial plane in Earth's outer radiation belt. We observed the microbursts on March 31st, 2017 with the Magnetic Electron Ion Spectrometer and RBSP Ion Composition Experiment on the Van Allen Probes. Microburst electrons with kinetic energies of 29‐92 keV were scattered over a substantial range of pitch angles, and over time intervals of 150‐500 ms. Furthermore, the microbursts arrived without dispersion in energy, indicating that they were recently scattered near the spacecraft. We have applied the relativistic theory of wave‐particle resonant diffusion to the calculated phase space density, revealing that the observed transport of microburst electrons is not consistent with the hypothesized quasi‐linear ap. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078451 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078451
More Details
2017
Authors: Cohen Ian J., Mitchell Donald G., Kistler Lynn M., Mauk Barry H., Anderson Brian J., et al.
Title: Dominance of high energy (>150 keV) heavy ion intensities in Earth's middle to outer magnetosphere
Abstract: Previous observations have driven the prevailing assumption in the field that energetic ions measured by an instrument using a bare solid state detector (SSD) are predominantly protons. However, new near-equatorial energetic particle observations obtained between 7 and 12 RE during Phase 1 of the Magnetospheric Multiscale (MMS) mission challenge the validity of this assumption. In particular, measurements by the Energetic Ion Spectrometer (EIS) instruments have revealed that the intensities of heavy ion species (specifically oxygen and helium) dominate those of protons at energies math formula150-220 keV in the middle to outer (>7 RE) magnetosphere. Given that relative composition measurements can drift as sensors degrade in gain, quality cross-calibration agreement between EIS observation. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024351 Available at: onlinelibrary.wiley.com/doi/10.1002/2017JA024351/full
More Details
2015
Authors: Reeves Geoffrey D, Friedel Reiner H W, Larsen Brian A., Skoug Ruth M., Funsten Herbert O., et al.
Title: Energy dependent dynamics of keV to MeV electrons in the inner zone, outer zone, and slot regions.
Abstract: We present observations of the radiation belts from the HOPE and MagEIS particle detectors on the Van Allen Probes satellites that illustrate the energy-dependence and L-shell dependence of radiation belt enhancements and decays. We survey events in 2013 and analyze an event on March 1 in more detail. The observations show: (a) At all L-shells, lower-energy electrons are enhanced more often than higher energies; (b) Events that fill the slot region are more common at lower energies; (c) Enhancements of electrons in the inner zone are more common at lower energies; and (d) Even when events do not fully fill the slot region, enhancements at lower-energies tend to extend to lower L-shells than higher energies. During enhancement events the outer zone extends to lower L-shells at lower energie. . .
Date: 12/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021569 Available at: http://doi.wiley.com/10.1002/2015JA021569http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021569
More Details
Authors: Dai Lei, Wang Chi, Duan Suping, He Zhaohai, Wygant John R., et al.
Title: Near-Earth Injection of MeV Electrons associated with Intense Dipolarization Electric Fields: Van Allen Probes observations
Abstract: Substorms generally inject 10s-100s keV electrons, but intense substorm electric fields have been shown to inject MeV electrons as well. An intriguing question is whether such MeV electron injections can populate the outer radiation belt. Here we present observations of a substorm injection of MeV electrons into the inner magnetosphere. In the pre-midnight sector at L∼5.5, Van Allen Probes (RBSP)-A observed a large dipolarization electric field (50mV/m) over ∼40s and a dispersionless injection of electrons up to ∼3 MeV. Pitch angle observations indicated betatron acceleration of MeV electrons at the dipolarization front. Corresponding signals of MeV electron injection were observed at LANL-GEO, THEMIS-D, and GOES at geosynchronous altitude. Through a series of dipolarizations, the in. . .
Date: 07/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL064955 Available at: http://doi.wiley.com/10.1002/2015GL064955
More Details
2014
Authors: Ozeke Louis G., Mann Ian R., Turner Drew L, Murphy Kyle R., Degeling Alex W., et al.
Title: Modeling cross L shell impacts of magnetopause shadowing and ULF wave radial diffusion in the Van Allen belts
Abstract: We present simulations of the outer electron radiation belt using a new ULF wave-driven radial diffusion model, including empirical representations of loss due to chorus and plasmaspheric hiss. With an outer boundary condition constrained by in situ electron flux observations, we focus on the impacts of magnetopause shadowing and outward radial diffusion in the heart of the radiation belt. Third invariant conserving solutions are combined to simulate the L shell and time dependence of the differential flux at a fixed energy. Results for the geomagnetically quiet year of 2008 demonstrate not only remarkable cross L shell impacts from magnetopause shadowing but also excellent agreement with the in situ observations even though no internal acceleration source is included in the model. Our mod. . .
Date: 10/2014 Publisher: Geophysical Research Letters Pages: 6556 - 6562 DOI: 10.1002/2014GL060787 Available at: http://doi.wiley.com/10.1002/grl.v41.19http://doi.wiley.com/10.1002/2014GL060787
More Details
Authors: Schiller Quintin, Li Xinlin, Blum Lauren, Tu Weichao, Turner Drew L, et al.
Title: A nonstorm time enhancement of relativistic electrons in the outer radiation belt
Abstract: Despite the lack of a geomagnetic storm (based on the Dst index), relativistic electron fluxes were enhanced over 2.5 orders of magnitude in the outer radiation belt in 13 h on 13–14 January 2013. The unusual enhancement was observed by Magnetic Electron Ion Spectrometer (MagEIS), onboard the Van Allen Probes; Relativistic Electron and Proton Telescope Integrated Little Experiment, onboard the Colorado Student Space Weather Experiment; and Solid State Telescope, onboard Time History of Events and Macroscale Interactions during Substorms (THEMIS). Analyses of MagEIS phase space density (PSD) profiles show a positive outward radial gradient from 4 < L < 5.5. However, THEMIS observations show a peak in PSD outside of the Van Allen Probes' apogee, which suggest a very interesting s. . .
Date: 01/2014 Publisher: Geophysical Research Letters Pages: 7 - 12 DOI: 10.1002/2013GL058485 Available at: http://doi.wiley.com/10.1002/2013GL058485
More Details
Authors: Turner Drew L
Title: Space science: Near-Earth space shows its stripes
Abstract: Using some of the first scientific satellites put into orbit during the late 1950s, teams led by physicists James Van Allen in the United States and Sergei Vernov in the Soviet Union independently reported1, 2 on defined regions of radiation in near-Earth space. These regions came to be known as Earth's radiation belts, and they represent the first major scientific discovery of the space age. However, despite decades of study, many questions in radiation-belt physics remain unanswered, mostly concerning the nature of the inner and outer belts, which are populated by electrons moving at near the speed of light. As society becomes ever more dependent on satellite-based technology, it is increasingly important to understand the variability in the radiation belts, because the highest-energy . . .
Date: 03/2014 Publisher: Nature Pages: 308 - 309 DOI: 10.1038/507308a Available at: http://www.nature.com/doifinder/10.1038/507308a
More Details
2013
Authors: Shprits Yuri Y, Subbotin Dmitriy, Drozdov Alexander, Usanova Maria E., Kellerman Adam, et al.
Title: Unusual stable trapping of the ultrarelativistic electrons in the Van Allen radiation belts
Abstract: Radiation in space was the first discovery of the space age. Earth’s radiation belts consist of energetic particles that are trapped by the geomagnetic field and encircle the planet1. The electron radiation belts usually form a two-zone structure with a stable inner zone and a highly variable outer zone, which forms and disappears owing to wave–particle interactions on the timescale of a day, and is strongly influenced by the very-low-frequency plasma waves. Recent observations revealed a third radiation zone at ultrarelativistic energies2, with the additional medium narrow belt (long-lived ring) persisting for approximately 4 weeks. This new ring resulted from a combination of electron losses to the interplanetary medium and scattering by electromagnetic ion cyclotron waves to the Ear. . .
Date: 11/2013 Publisher: Nature Physics Pages: 699 - 703 DOI: 10.1038/nphys2760 Available at: http://www.nature.com/doifinder/10.1038/nphys2760
More Details
2012
Authors: Turner Drew L, Shprits Yuri, Hartinger Michael, and Angelopoulos Vassilis
Title: Explaining sudden losses of outer radiation belt electrons during geomagnetic storms
Abstract: The Van Allen radiation belts were first discovered in 1958 by the Explorer series of spacecraft1. The dynamic outer belt consists primarily of relativistic electrons trapped by the Earth’s magnetic field. Magnetospheric processes driven by the solar wind2 cause the electron flux in this belt to fluctuate substantially over timescales ranging from minutes to years3. The most dramatic of these events are known as flux ’dropouts’ and often occur during geomagnetic storms. During such an event the electron flux can drop by several orders of magnitude in just a few hours4, 5 and remain low even after a storm has abated. Various solar wind phenomena, including coronal mass ejections and co-rotating interaction regions6, can drive storm activity, but several outstanding questions remain co. . .
Date: 01/2012 Publisher: Nature Publishing Group Pages: 208–212 DOI: 10.1038/nphys2185 Available at: http://dx.doi.org/10.1038/nphys2185
More Details