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- Nemec, F.Charles Univ Prague, Fac Math & Phys, Prague, Czech Republic (author)
Oblique Reflections of Mars Express MARSIS Radar Signals From Ionospheric Density Structures : Raytracing Analysis
- Article/chapterEnglish2019
Publisher, publication year, extent ...
- AMER GEOPHYSICAL UNION,2019
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- LIBRIS-ID:oai:DiVA.org:uu-390047
- https://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-390047URI
- https://doi.org/10.1029/2018JE005891DOI
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- Language:English
- Summary in:English
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- Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) radar sounder on board the Mars Express spacecraft revealed oblique reflections coming systematically from apparently stable density structures in the Martian ionosphere. Although these were typically interpreted by assuming a straight line propagation of the sounding signal at the speed of light, the ionospheric plasma is clearly a dispersive medium. Consequently, the ray propagation paths may be significantly bent, and, moreover, the observed time delays need to be interpreted in terms of realistic group velocities of the signal propagation. We select a single particularly well-pronounced event with oblique reflections observable over a large range of signal frequencies, and we employ raytracing calculations to perform its detailed analysis. An isolated density structure responsible for the reflection of the sounding signal back to the spacecraft is assumed, and the relevant ionospheric signal propagation is properly evaluated. We show that initially oblique sounding signals get progressively more oblique during their propagation, imposing an upper threshold on the angular propagation distance between the spacecraft and the reflecting density structure, in line with the observations. Considering realistic propagation paths further allows us to explain the frequency dependence of the observed time delays and to accurately model the entire event. The obtained results are consistent with the spacecraft passing very close to a spatially limited density structure. We also show that the results obtained using realistic raytracing calculations are significantly different from the results obtained using additional simplifying assumptions.
Subject headings and genre
- NATURVETENSKAP Fysik Fusion, plasma och rymdfysik hsv//swe
- NATURAL SCIENCES Physical Sciences Fusion, Plasma and Space Physics hsv//eng
- MARSIS
- Mars Express
- Martian ionosphere
Added entries (persons, corporate bodies, meetings, titles ...)
- Andrews, David J.Uppsala universitet,Institutet för rymdfysik, Uppsalaavdelningen(Swepub:uu)davan153 (author)
- Morgan, D. D.Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA (author)
- Kopf, A. J.Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA (author)
- Gurnett, D. A.Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA (author)
- Charles Univ Prague, Fac Math & Phys, Prague, Czech RepublicInstitutet för rymdfysik, Uppsalaavdelningen (creator_code:org_t)
Related titles
- In:Journal of Geophysical Research - Planets: AMER GEOPHYSICAL UNION124:5, s. 1177-11872169-90972169-9100
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