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- Title
Seasonal and Geographical Variability of the Martian Ionosphere From Mars Express Observations.
- Authors
González‐Galindo, F.; Eusebio, D.; Němec, F.; Peter, K.; Kopf, A.; Tellmann, S.; Paetzold, M.
- Abstract
We study the seasonal and geographical variability of the peak electron density and the altitude of the main ionospheric peak at Mars. For this purpose, we use the data obtained by the ESA Mars Express mission, namely by the radar MARSIS and the radio occultation experiment MaRS. The accumulation of data during the long lifetime of Mars Express provides for the first time an almost complete seasonal and geographical coverage. We first remove the dominant variability factors affecting the main ionospheric peak, namely the effect of changes in the solar zenith angle (SZA), and the changes in the solar ultraviolet radiation output at the Sun. When averaging results obtained at all latitudes, we find that the seasonal variation of both the peak density and the peak altitude can be well reproduced by sinusoidal functions with amplitudes about 8%–9% of the annually averaged peak density, and between 8 and 9.5 km for the peak altitude. We also find elevated peak electron densities in the region of strong crustal fields and latitudinal asymmetries in both the peak density and altitude. Comparing the seasonal evolution of the peak altitude during Mars Year 28, a year with a global dust storm, and the rest of the years, we find that the global dust storm raised the altitude of the ionospheric peak by about 10–15 km. Plain Language Summary: The ionosphere is the atmospheric region where solar ultraviolet radiation breaks molecules and atoms into ions and electrons. At Mars dayside, the electron density profiles display a well‐defined peak at average altitude of about 130 km. The electron concentration at the peak and the altitude of the peak are strongly affected by changes in the illumination conditions and the solar radiation. Here we study the variability induced by the eccentricity of the Martian orbit with data accumulated by the Mars Express mission during more than 10 terrestrial years, offering for the first time an almost complete seasonal and geographical coverage. We find that the changes in peak density and peak altitude with Mars seasons can be well represented by sinusoidal functions, with their minima and maxima well aligned with the timing of the maximum and minimum distance from the Sun. We have also studied possible geographical variations, finding that the peak density increases in a region with a remnant magnetic field, due to the interaction of the solar wind and these fields. We also find that a global dust storm induced a significant increase of the peak altitude due to the heating of the suspended dust by solar radiation. Key Points: The seasonal and geographical variability of the Martian ionosphere are studied with Mars Express data offering an unprecedented coverageSeasonal variability of ionospheric peak is well fitted by sinusoidal functions with maxima and minima at Mars aphelion and perihelionExternal influences such as a global dust storm or the presence of crustal fields affect the ionospheric peak
- Subjects
ELECTRON density; MARTIAN ionosphere; MARTIAN exploration; MARS Express (Spacecraft); SPACE exploration
- Publication
Journal of Geophysical Research. Planets, 2021, Vol 126, Issue 2, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2020JE006661