Biblio

Found 4 results
Filters: Author is Averkamp, T. F.  [Clear All Filters]
2017
Authors: Hartley D. P., Kletzing C A, Kurth W S, Hospodarsky G B, Bounds S R, et al.
Title: An improved sheath impedance model for the Van Allen probes EFW instrument: Effects of the spin axis antenna
Abstract: A technique to quantitatively determine the sheath impedance of the Van Allen Probes Electric Field and Waves (EFW) instrument is presented. This is achieved, for whistler mode waves, through a comparison between the total electric field wave power spectra calculated from magnetic field observations and cold plasma theory, and the total electric field wave power measured by the EFW spherical double probes instrument. In a previous study, a simple density-dependent sheath impedance model was developed in order to account for the differences between the observed and calculated wave electric field. The current study builds on this previous work by investigating the remaining discrepancies, identifying their cause, and developing an improved sheath impedance correction. Analysis reveals that a. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023597 Available at: http://doi.wiley.com/10.1002/2016JA023597
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2016
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
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2014
Authors: Santolik O, Hospodarsky G B, Kurth W S, Averkamp T. F., Kletzing C A, et al.
Title: Statistical properties of wave vector directions of whistler-mode waves in the radiation belts based on measurements of the Van Allen probes and Cluster missions
Abstract: Wave-particle interactions in the Earth's Van Allen radiation belts are known to be an efficient process of the exchange of energy between different particle populations, including the energetic radiation belt particles. The whistler mode waves, especially chorus, can control the radiation belt dynamics via linear or nonlinear interactions with both the energetic radiation belt electrons and lower energy electron populations. Wave vector directions are a very important parameter of these wave-particle interactions. We use measurements of whistlermode waves by the WAVES instrument from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard the Van Allen Probes spacecraft covering the equatorial region of the Earth's magnetosphere in all MLT sectors, and a . . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929880 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929880
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Authors: Menietti J. D., Averkamp T. F., Groene J. B., Horne R B, Shprits Y Y, et al.
Title: Survey analysis of chorus intensity at Saturn
Abstract: In order to conduct theoretical studies or modeling of pitch angle scattering of electrons by whistler mode chorus emission at Saturn, a knowledge of chorus occurrence and magnetic intensity levels, PB, as well as the distribution of PB relative to frequency and spatial parameters is essential. In this paper an extensive survey of whistler mode magnetic intensity levels at Saturn is carried out, and Gaussian fits of PB are performed. We fit the spectrum of wave magnetic intensity between the lower hybrid frequency and fceq/2 and for frequencies in the interval fceq/2 < f < 0.9 fceq, where fceq is the cyclotron frequency mapped to the equator. Saturn chorus is observed over most local times, but is dominant on the nightside in the range of 4.5 < L <7.5, with minimum power at t. . .
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 8415 - 8425 DOI: 10.1002/jgra.v119.1010.1002/2014JA020523 Available at: http://doi.wiley.com/10.1002/jgra.v119.10http://doi.wiley.com/10.1002/2014JA020523
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