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The variability of the topside ionospheres of Venus and Mars

Presentation #211.03 in the session Planetary Space Physics (Poster + Lightning Talk)

Published onOct 23, 2023
The variability of the topside ionospheres of Venus and Mars

The orbital and environmental parameters of Venus and Mars show significant differences (e.g. in orbit-Sun-distance, planetary mass/diameter, rotation rate, surface pressure). Their planetary ionospheres, however, display notable similarities. The photochemically dominated regions of the undisturbed dayside ionospheres of Venus and Mars are both characterized by two major features: the ionospheric main peak region (designated as V2 at Venus and M2 at Mars) is a result from photoionization by solar EUV radiation, while the weaker secondary V1/M1 region originates from the primary and secondary ionization of the neutral atmosphere caused by solar X-ray radiation [1]. The upper region of the Venus and Mars dayside ionospheres is governed by transport processes. The extent and shape of the ionospheric topsides observed with Venus Express Radio Science (VEX-VeRa) and Mars Express Radio Science (MEX-MaRS) observations exhibit substantial variability on temporal scales and ranges from an undisturbed exponential decay to strongly compressed shapes.

This study utilizes 9 years of VEX-VeRa (2006-2014) and 18 years of MEX-MaRS (2004-ongoing) radio science observations to investigate the behavior of the upper ionospheric region of Venus and Mars. The identified ionospheric parameters will be compared to characteristics of the solar wind interaction region / plasma boundaries of both planets identified by Venus Express [2], Mars Express [3] and MAVEN [4] to improve our understanding of the solar wind interaction of planets without a global magnetic field. The effect of potential drivers on the temporal variability of the upper ionosphere are investigated for Venus and Mars by comparison with pristine solar wind parameters (e.g. VEX-ASPERA4 [5], MEX-ASPERA3 [6]) and solar radiation fluxes (FISM-V2 model [7], MAVEN EUV monitor [8]).

References

[1] Fox et al. (1996) Adv. Space Res., 17 (11)

[2] Titov et al. (2006) Cosmic Research 44 (4)

[3] Fletcher (2004) Mars Express. The scientific payload. ESA

[4] Jakosky B. M. et al. (2015) SSR, 195, 3-48

[5] Barabash et al. (2007) PSS, 55 (12)

[6] Barabash et al. (2006) SSR, 126, 113-164

[7] Chamberlin et al. (2020) Space Weather, 18 (12)

[8] Thiemann et al. (2017) JGR Space Phys., 122 (3)

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