Oblique Reflections of Mars Express MARSIS Radar Signals From Ionospheric Density Structures: Raytracing Analysis

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F19%3A10405824" target="_blank" >RIV/00216208:11320/19:10405824 - isvavai.cz</a>

Výsledek na webu

<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=9XC73sT9ET" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=9XC73sT9ET</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1029/2018JE005891" target="_blank" >10.1029/2018JE005891</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Oblique Reflections of Mars Express MARSIS Radar Signals From Ionospheric Density Structures: Raytracing Analysis

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

Oblique Reflections of Mars Express MARSIS Radar Signals From Ionospheric Density Structures: Raytracing Analysis

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10305 - Fluids and plasma physics (including surface physics)

Projekt

<a href="/cs/project/LTAUSA17070" target="_blank" >LTAUSA17070: Elektromagnetické vlny v planetárních ionosférách a magnetosférách</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)<br>I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Journal of Geophysical Research: Planets

ISSN

2169-9097

e-ISSN

—

Svazek periodika

124

Číslo periodika v rámci svazku

5

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

11

Strana od-do

1177-1187

Kód UT WoS článku

000471600600003

EID výsledku v databázi Scopus

2-s2.0-85065245074