Journal article
Using the cold plasma dispersion relation and whistler mode waves to quantify the antenna sheath impedance of the Van Allen Probes EFW instrument
Journal of geophysical research. Space physics, Vol.121(5), pp.4590-4606
05/2016
DOI: 10.1002/2016JA022501
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/ calculated); the percentage of overestimates decreases, the percentage of underestimates increases, and the spread of values is significantly reduced. Calculated plasmaspheric hiss wave powers are, on average, a good estimate of those observed, whereas calculated chorus wave powers are persistently and systematically underestimated. Investigation of wave power ratios (observed/calculated), as a function of frequency and plasma density, reveals a structure consistent with signal attenuation via the formation of a plasma sheath around the Electric Field and Waves spherical double probes instrument. A simple, density‐dependent model is developed in order to quantify this effect of variable impedance between the electric field antenna and the plasma interface. This sheath impedance model is then demonstrated to be successful in significantly improving agreement between calculated and observed power spectra and wave powers.
Key Points
Whistler mode wave power is compared to that calculated assuming cold plasma theory and including wave normal angle
Structure of discrepancies consistent with variable sheath impedance between EFW electric field antenna and plasma
Sheath impedance model is developed and shown to be successful in quantifying sheath impedance of EFW instrument
Details
- Title: Subtitle
- Using the cold plasma dispersion relation and whistler mode waves to quantify the antenna sheath impedance of the Van Allen Probes EFW instrument
- Creators
- D. P Hartley - University of IowaC. A Kletzing - University of IowaW. S Kurth - University of IowaS. R Bounds - University of IowaT. F Averkamp - University of IowaG. B Hospodarsky - University of IowaJ. R Wygant - University of MinnesotaJ. W Bonnell - University of California, BerkeleyO Santolík - Charles UniversityC. E. J Watt - University of Reading
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.121(5), pp.4590-4606
- DOI
- 10.1002/2016JA022501
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 17
- Grant note
- Praemium Academiae STFC (ST/M000885/1) JHU/APL (921647) NASA Prime (NAS5-01072; LH14010; LH15304)
- Language
- English
- Date published
- 05/2016
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984200038802771
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