The dayside ionosphere of Mars: Comparing a one-dimensional photochemical model with MAVEN Deep Dip campaign observations

Mukundan, Vrinda; Thampi, Smitha V.; Bhardwaj, Anil; Krishnaprasad, C.

doi:10.1016/j.icarus.2019.113502

Cited by 14 publications

(49 citation statements)

References 44 publications

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“…For the altitude range displayed in Figure 1b, the condition of local energy degradation is a reasonable approximation (e.g., Wu, Cui, Cao, Sun, et al, 2019), which facilitates greatly the calculation of the photoelectron intensity in the Martian ionosphere with the aid of the analytical yield spectrum (AYS) method. Such a method was recently used by Mukundan et al (2020), who reported a good agreement between the model photoelectron spectra and the SWEA measurements over the energy range of 10-250 eV…”

Section: Analytical Yield Spectrum Modeling Resultsmentioning

confidence: 99%

“…Such a method was recently used by Mukundan et al. (2020), who reported a good agreement between the model photoelectron spectra and the SWEA measurements over the energy range of 10–250 eV without the need to adjust the solar EUV and X‐ray irradiance inferred from the MAVEN Extreme Ultraviolet Monitor band irradiance data (Thiemann et al., 2017). The AYS method has the advantage of isolating the nonspatial information of the photoelectron degradation processes and incorporating photoelectron production via downward degradation from more energetic states with a parametrized two‐dimensional matrix (Green et al., 1977).…”

Section: Analytical Yield Spectrum Modeling Resultsmentioning

confidence: 99%

“…By employing simple AYS model calculations (e.g., Mukundan et al., 2020), we derive the altitude variation of photoelectron intensity at representative energies based on different choices of the background atmosphere. We find that the presence of CO is crucial for reproducing the observations, and such an interesting finding is mainly due to enhanced inelastic collisions of photoelectrons with CO at 10–15 eV when compared to collisions with CO 2 (Brunger & Buckman, 2002).…”

Section: Resultsmentioning

confidence: 99%

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Photoelectrons as a Tracer of Planetary Atmospheric Composition: Application to CO on Mars

Cui

Yelle

et al. 2020

JGR Planets

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Photoelectrons are an extensively studied component of planetary ionospheres which have been frequently used as a diagnostic of ambient magnetic fields. We show in this study that they also provide information on atmospheric composition via the altitude variation of photoelectron intensity at specific energies. Such an idea is applied to Mars for which a large observational sample of photoelectrons is available from the Solar Wind Electron Analyzer measurements made by the Mars Atmosphere and Volatile Evolution (MAVEN). Our analysis reveals a strong decline in photoelectron intensity from 160 to 200 km, but this trend is restricted to a narrow energy range of 10–15 eV. By employing analytical yield spectrum calculations, we derive the model variations based on different choices of the background atmosphere. We find that the presence of CO is crucial for reproducing the observed variations. This allows atmospheric CO densities to be estimated from photoelectron measurements, which are a factor of 3–7 lower than the published densities based on the MAVEN Neutral Gas and Ion Mass Spectrometer measurements and in better agreement with existing model results. In general, the usefulness of photoelectron intensity at a specific energy as a tracer of atmospheric composition relies critically on the species‐dependent inelastic electron impact cross section at this energy.

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Section: Analytical Yield Spectrum Modeling Resultsmentioning

confidence: 99%

Section: Analytical Yield Spectrum Modeling Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Photoelectrons as a Tracer of Planetary Atmospheric Composition: Application to CO on Mars

Cui

Yelle

et al. 2020

JGR Planets

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“…The effect of ambient magnetic fields on the Martian ionosphere occurs mainly via modification of plasma diffusion (e.g., Matta et al, 2015; Shinagawa & Cravens, 1989). Below 200 km, the effect of diffusion is usually negligible (e.g., Mendillo et al, 2011; Mukundan et al, 2020), which is responsible for the absence of magnetic control at these altitudes in Figure 9. At higher altitudes, the effect of diffusion is critically dependent on the ambient magnetic field configuration.…”

Section: Magnetic Control Of Minor Ion Peak Parametersmentioning

confidence: 99%

“…For demonstrative purposes, we take O + as an example without loss of generality and examine its density variation with altitude in the dayside Martian ionosphere. When photochemistry dominates, production of O + via photoionization of O is roughly balanced by destruction of O + via its reaction with background CO 2 , which further implies an increase in O + density with increasing altitude since O is lighter than CO 2 (e.g., Mukundan et al, 2020). This trend continues to sufficiently high altitudes until other light neutral species such as H 2 become more abundant than CO 2 (e.g., Fox, 2003).…”

Section: Parameterization Of Minor Ion Peaksmentioning

confidence: 99%

Solar and Magnetic Control of Minor Ion Peaks in the Dayside Martian Ionosphere

Huang

Cui

Hao³

et al. 2020

JGR Space Physics

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The Neutral Gas and Ion Mass Spectrometer of the Mars Atmosphere and Volatile Evolution provides a large data set to explore the ion composition and structure of the Martian ionosphere. Here, the dayside measurements are used to investigate the minor ion density profiles with distinctive peaks above 150 km, revealing a systematic trend of decreasing peak altitude with increasing ion mass. We specifically focus on a subset of species including O+, N 2+/CO+, C+, N+, He+, and O++, all of which are mainly produced via direct photoionization of parent neutrals. Our analysis reveals weak or no variation with solar zenith angle (SZA) in both peak density and altitude, which is an expected result because these ion peaks are located within the optically thin regions subject to the same level of solar irradiance independent of SZA. In contrast, the solar cycle variations of peak density and altitude increase considerably with increasing solar activity, as a result of enhanced photoionization frequency and atmospheric expansion at high solar activities. He+ serves as an exception in that its peak density increases toward large SZA and meanwhile shows no systematic variation with solar activity. The thermospheric He distribution on Mars should play an important role in determining these observed variations. Finally, the peak altitudes for all species are elevated by at least several km within the weakly magnetized regions, possibly attributable to the suppression of vertical diffusion by preferentially horizontal magnetic fields in these regions.

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Ionization Sources of Upper Ionosphere of Mars

Haider

2023

Astrophysics and Space Science Library

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The dayside ionosphere of Mars: Comparing a one-dimensional photochemical model with MAVEN Deep Dip campaign observations

Cited by 14 publications

References 44 publications

Photoelectrons as a Tracer of Planetary Atmospheric Composition: Application to CO on Mars

Photoelectrons as a Tracer of Planetary Atmospheric Composition: Application to CO on Mars

Solar and Magnetic Control of Minor Ion Peaks in the Dayside Martian Ionosphere

Ionization Sources of Upper Ionosphere of Mars

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