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Found 4 results
Filters: Author is C. A. Kletzing  [Clear All Filters]
2017
Authors: Chen X.-R., Zong Q.-G., Zhou X.-Z., Blake Bernard, Wygant J. 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 ultralow frequency (ULF) waves on 29 October 2013. Oscillations in electron flux were observed at the period of ∼450 s, which is also the dominant period of the observed ULF magnetic pulsations. The phase shift of the electron fluxes (∼50 to 150 keV) across the estimated resonant energy (∼104 keV) is ∼360°. 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 p. . .
Date: 02/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL071252 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071252/full
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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 nonlinear interactions with VLF chorus
Abstract: Prompt recovery of MeV (millions of electron Volts) electron populations in the poststorm 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 nonlinear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant nonadiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of nonlinear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy of hundreds of keV to 3 MeV can be a. . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023429 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023429
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Authors: Woodroffe J. R., Jordanova V. K., Funsten H. O., Streltsov A. V., Bengtson M. T., et al.
Title: Van Allen Probes Observations of Structured Whistler-mode Activity and Coincident Electron Landau Acceleration Inside a Remnant Plasmaspheric Plume
Abstract: We present observations from the Van Allen Probes spacecraft that identify an region of intense whistler-mode activity within a large density enhancement outside of the plasmasphere. We speculate that this density enhancement is part of a remnant plasmaspheric plume, with the observed wave being driven by a weakly anisotropic electron injection that drifted into the plume and became non-linearly unstable to whistler emission. Particle measurements indicate that a significant fraction of thermal (<100 eV) electrons within the plume were subject to Landau acceleration by these waves, an effect that is naturally explained by whistler emission within a gradient and high-density ducting inside a density enhancement.
Date: 02/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA022219 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA022219/full
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Authors: Li J., Bortnik J., Li W., Ma Q., Thorne R. M., et al.
Title: “Zipper-like” periodic magnetosonic waves: Van Allen Probes, THEMIS, and magnetospheric multiscale observations
Abstract: An interesting form of “zipper-like” magnetosonic waves consisting of two bands of interleaved periodic rising-tone spectra was newly observed by the Van Allen Probes, the Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Magnetospheric Multiscale (MMS) missions. The two discrete bands are distinct in frequency and intensity; however, they maintain the same periodicity which varies in space and time, suggesting that they possibly originate from one single source intrinsically. In one event, the zipper-like magnetosonic waves exhibit the same periodicity as a constant-frequency magnetosonic wave and an electrostatic emission, but the modulation comes from neither density fluctuations nor ULF waves. A statistical survey based on 3.5 years of multisat. . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023536 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023536
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