Structure and composition of the neutral upper atmosphere of Mars from the MAVEN NGIMS investigation

Mahaffy, P. R.; Benna, M.; Elrod, M. K.; Yelle, R. V.; Bougher, S. W.; Stone, Shane; Jakosky, B. M.

doi:10.1002/2015gl065329

Cited by 183 publications

(213 citation statements)

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“…Both ionization efficiencies remain roughly constant above 160km, with median values of 0.19±0.03 for CO 2 and 0.27±0.04 for O. For comparison, the model results of Nicholson et al (2009), shown with the blue lines in Figure 2 and appropriate for a median SZA of 55°, predict This should be compared to the MAVEN-based CO 2 ionization efficiency of 0.19 as CO 2 is the most abundant species at this altitude (Mahaffy et al 2015a). The above comparisons indicate that a fair data-model agreement could be achieved in terms of the magnitude of the ionization efficiency at the top of the atmosphere.…”

Section: Magnitudes and Trends Of Ionization Efficiencymentioning

confidence: 99%

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Ionization Efficiency in the Dayside Martian Upper Atmosphere

Cui

et al. 2018

ApJL

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Combining the Mars Atmosphere and Volatile Evolution measurements of neutral atmospheric density, solar EUV/X-ray flux, and differential photoelectron intensity made during 240 nominal orbits, we calculate the ionization efficiency, defined as the ratio of the secondary (photoelectron impact) ionization rate to the primary (photon impact) ionization rate, in the dayside Martian upper atmosphere under a range of solar illumination conditions. Both the CO 2 and O ionization efficiencies tend to be constant from 160km up to 250km, with respective median values of 0.19±0.03 and 0.27±0.04. These values are useful for fast calculation of the ionization rate in the dayside Martian upper atmosphere, without the need to construct photoelectron transport models. No substantial diurnal and solar cycle variations can be identified, except for a marginal trend of reduced ionization efficiency approaching the terminator. These observations are favorably interpreted by a simple scenario with ionization efficiencies, as a first approximation, determined by a comparison between relevant cross sections. Our analysis further reveals a connection between regions with strong crustal magnetic fields and regions with high ionization efficiencies, which are likely indicative of more efficient vertical transport of photoelectrons near magnetic anomalies.

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Section: Magnitudes and Trends Of Ionization Efficiencymentioning

confidence: 99%

“…The summation in Equation (3) is over CO 2 and O, the two most abundant neutral species in the Martian upper atmosphere (Mahaffy et al 2015a). The respective crosssection data, s…”

Section: Calculation Of Ionization Efficiencymentioning

confidence: 99%

Ionization Efficiency in the Dayside Martian Upper Atmosphere

Cui

et al. 2018

ApJL

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“…The role of solar forcing has been confirmed by a number of authors using the data from the drag experiments made on board Mars Global Surveyor (Forbes et al 2008;Krasnopolsky 2010), and the data acquired by the Neutral Gas and Ion Mass Spectrometer (NGIMS), the Accelerometer, as well as the Imaging Ultraviolet Spectrograph on board the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft (Jain et al 2015;Mahaffy et al 2015a;Bougher et al 2017;Zurek et al 2017).…”

Section: Introductionmentioning

confidence: 84%

The Impact of Crustal Magnetic Fields on the Thermal Structure of the Martian Upper Atmosphere

Cui

Yelle

Zhao

et al. 2018

ApJL

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Using the Mars Atmosphere and Volatile Evolution Neutral Gas and Ion Mass Spectrometer data, we investigate the possible impact of crustal magnetic fields on the thermal structure of the Martian upper atmosphere. Our analysis reveals a clear enhancement in temperature over regions with strong crustal magnetic fields during two deep dip campaigns covering the periods of April 17-22 and September 2-8, both in 2015. Several controlling factors, such as solar EUV irradiance, relative atomic O abundance, and non-migrating tides, do not help to explain the observed temperature enhancement, and a magnetically driven scenario is favored. We evaluate the roles of several heating mechanisms that are likely modulated by the presence of crustal magnetic fields, including Joule heating, ion chemical heating, as well as electron impact heating via either precipitating solar wind electrons or locally produced photoelectrons. The respective heating rates of these mechanisms are substantially lower than the solar EUV heating rate, implying that none of them is able to interpret the observations.

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“…With a conservative estimate that the efficiency of escape is 10%, the ion escape rate ranges from ∼10 32 ions for protons from supernova at 100 pc to ∼10 41 ions for the interstellar cloud scenario. We also carried out simulations with the present atmospheric composition (Mahaffy et al 2015) with higher concentration of oxygen in the upper atmosphere. The results indicate higher escape rates as shown in the table.…”

Section: Resultsmentioning

confidence: 99%

Did high-energy astrophysical sources contribute to Martian atmospheric loss?

Atri¹

2016

Monthly Notices of the Royal Astronomical Society: Letters

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Mars is believed to have had a substantial atmosphere in the past. Atmospheric loss led to depressurization and cooling, and is thought to be the primary driving force responsible for the loss of liquid water from its surface. Recently, MAVEN observations have provided new insight into the physics of atmospheric loss induced by ICMEs and solar wind interacting with the Martian atmosphere. In addition to solar radiation, it is likely that its atmosphere has been exposed to radiation bursts from high-energy astrophysical sources which become highly probable on timescales of ∼Gy and beyond. These sources are capable of significantly enhancing the rates of photoionization and charged particle-induced ionization in the upper atmosphere. We use Monte Carlo simulations to model the interaction of charged particles and photons from astrophysical sources in the upper Martian atmosphere and discuss its implications on atmospheric loss. Our calculations suggest that the passage of the solar system though dense interstellar clouds is the most significant contributor to atmospheric loss among the sources considered here.

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Structure and composition of the neutral upper atmosphere of Mars from the MAVEN NGIMS investigation

Cited by 183 publications

References 10 publications

Ionization Efficiency in the Dayside Martian Upper Atmosphere

Ionization Efficiency in the Dayside Martian Upper Atmosphere

The Impact of Crustal Magnetic Fields on the Thermal Structure of the Martian Upper Atmosphere

Did high-energy astrophysical sources contribute to Martian atmospheric loss?

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