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Characterizing Average Electron Densities in the Martian Dayside Upper Ionosphere
Charles Univ Prague, Fac Math & Phys, Prague, Czech Republic.ORCID iD: 0000-0002-3233-2718
Univ Iowa, Dept Phys & Astron, Iowa City, IA USA.ORCID iD: 0000-0002-3343-9234
Univ Iowa, Dept Phys & Astron, Iowa City, IA USA.
Univ Iowa, Dept Phys & Astron, Iowa City, IA USA.ORCID iD: 0000-0003-2403-0282
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2019 (English)In: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 124, no 1, p. 76-93Article in journal (Refereed) Published
Abstract [en]

We use more than 10years of the Martian topside ionospheric data measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding radar sounder on board the Mars Express spacecraft to derive an empirical model of electron densities from the peak altitude up to 325km. Altogether, 16,044 electron density profiles obtained at spacecraft altitudes lower than 425km and at solar zenith angles lower than 80 degrees are included in the analysis. Each of the measured electron density profiles is accurately characterized by the peak electron density, peak altitude, and three additional parameters describing the profile shape above the peak: (i) steepness at high altitudes, (ii) main layer thickness, and (iii) transition altitude. The dependence of these parameters on relevant controlling factors (solar zenith angle, solar irradiance, crustal magnetic field magnitude, and Sun-Mars distance) is evaluated, allowing for a formulation of a simple empirical model. Mars Atmosphere and Volatile EvolutioN Extreme Ultraviolet monitor data are used to show that the solar ionizing flux can be accurately approximated by the F10.7 index when taking into account the solar rotation. Electron densities predicted by the resulting empirical model are compared with electron densities locally evaluated based on the Mars Advanced Radar for Subsurface and Ionosphere Sounding measurements, with the Langmuir Probe and Waves electron density measurements on board the Mars Atmosphere and Volatile EvolutioN spacecraft, and with electron densities obtained by radio occultation measurements. Although the electron densities measured by the Langmuir Probe and Waves instrument are systematically somewhat lower than the model electron densities, consistent with former findings, the model performs reasonably well.

Abstract [en]

Plain Language Summary

The ionosphere of Mars is the ionized part of its atmosphere, on the dayside ultimately controlled by the solar irradiation. Information about the electron density in there can be, among others, obtained by the radar sounding from a spacecraft orbiting the planet. Such measurements have been performed since 2005 by the Mars Advanced Radar for Subsurface and Ionosphere Sounding on board the Mars Express spacecraft, and they provide us with electron density profiles from the spacecraft altitude down to the altitude of the peak electron density. We use more than 10years of such measurements to develop an empirical model of typical ionospheric electron densities. The obtained results are compared with electron densities measured in situ by the Langmuir Probe and Waves instrument on board the MAVEN spacecraft available since 2014. A reasonable agreement between the model predictions and these independent observations is found. Finally, the analysis of solar radiation measured by Extreme Ultraviolet monitor on board the MAVEN spacecraft is used to show that, when the solar rotation is properly accounted for, the solar ionizing flux at Mars can be surprisingly well approximated by the solar radio flux measured at Earth.

Place, publisher, year, edition, pages
2019. Vol. 124, no 1, p. 76-93
Keywords [en]
MARSIS, MAVEN LPW, Mars ionosphere
National Category
Fusion, Plasma and Space Physics Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-378741DOI: 10.1029/2018JE005849ISI: 000459245700005OAI: oai:DiVA.org:uu-378741DiVA, id: diva2:1295210
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-11Bibliographically approved

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Andrews, David J.

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Němec, F.Morgan, David. D.Gurnett, D. A.Andrews, David J.Andersson, Laila
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Swedish Institute of Space Physics, Uppsala Division
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Journal of Geophysical Research - Planets
Fusion, Plasma and Space PhysicsAstronomy, Astrophysics and Cosmology

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