Ionization, luminosity, and heating of the upper atmosphere of Mars

Fox, Jane L.; Dalgarno, A.

doi:10.1029/ja084ia12p07315

Cited by 290 publications

(295 citation statements)

References 118 publications

Supporting

Mentioning

270

Contrasting

Unclassified

Order By: Relevance

“…Although it seems evident that concentrations of N 2 in the past were much higher than they are now [McElroy et al, 1976], new observations of N 2 on Mars would improve calculations of its escape rate and its evolution from primordial concentrations [Fox and Dalgarno, 1980;Fox, 1993]. These observations would be particularly valuable above about 120 km, where the upper atmosphere diffusively separates.…”

Section: Introductionmentioning

confidence: 99%

“…Relevant attributes of the observations used in this work are summarized in Table 1. Since the Martian dayglow is driven primarily by solar processes [e.g., Fox and Dalgarno, 1979], it is important to monitor the solar activity during the observations when comparing against model results. During the observations presented here, the Sun was moderately active with an F 10.7 radio flux of 171 solar flux units (1 SFU = 10 À22 W m À2 Hz À1 ) at one astronomical unit (AU).…”

Section: The Observationsmentioning

confidence: 99%

“…Leblanc et al [2006] reported a tentative identification of VK emission using limb observations from the Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) instrument on the Mars Express mission. Leblanc et al [2007] later determined that the SPICAM VK emission was about 3 times weaker than predicted by Fox and Dalgarno [1979], suggesting that Fox and Dalgarno had overestimated these emissions and that new calculations using more recent parameters may resolve the discrepancy. Fox and Hac [2013] updated the calculations using the latest molecular constants, cross sections, and solar irradiance models and determined that revised predictions of limb intensities were indeed consistent with SPICAM observations.…”

Section: Introductionmentioning

confidence: 99%

“…The relatively low abundance of molecular nitrogen (N 2 ) in the present Martian atmosphere has been a topic of great interest [e.g., Dalgarno and McElroy, 1970;Brinkmann, 1971;Fox, 1993]. Although it seems evident that concentrations of N 2 in the past were much higher than they are now [McElroy et al, 1976], new observations of N 2 on Mars would improve calculations of its escape rate and its evolution from primordial concentrations [Fox and Dalgarno, 1980;Fox, 1993].…”

Section: Introductionmentioning

confidence: 99%

“…Fox and Dalgarno [1979] predicted overhead intensities of a variety of N 2 bands and suggested that the photoelectron excited Vegard-Kaplan (VK) bands in the mid-UV (MUV) may be detectable. In practice, however, the measurement is challenging because the N 2 dayglow emission is weak relative to the bright and spectrally complex emissions arising primarily from processes on CO 2 that are present throughout the MUV [e.g., Jain et al, 2015].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

Stevens

Evans

Schneider

et al. 2015

Geophysical Research Letters

View full text Add to dashboard Cite

We identify molecular nitrogen (N2) emissions in the Martian upper atmosphere using the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We report the first observations of the N2 Lyman‐Birge‐Hopfield (LBH) bands at Mars and confirm the tentative identification of the N2 Vegard‐Kaplan (VK) bands. We retrieve N2 density profiles from the VK limb emissions and compare calculated limb radiances between 90 and 210 km against both observations and predictions from a Mars general circulation model (GCM). Contrary to earlier analyses using other satellite data, we find that N2 abundances exceed GCM results by about a factor of 2 at 130 km but are in agreement at 150 km. The analysis and interpretation are enabled by a linear regression method used to extract components of UV spectra from IUVS limb observations.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: The Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

Stevens

Evans

Schneider

et al. 2015

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

Intensities of the Venusian N₂ electron‐impact excited dayglow emissions

Fox

Hac

2013

JGR Space Physics

View full text Add to dashboard Cite

[1] Dayglow emissions are signatures of both the energy deposition into an atmosphere and the abundances of the species from which they arise. The first N 2 dayglow emissions from Mars, the (0,5) and (0,6) bands of the N 2 Vegard-Kaplan band system, were detected by the Spectroscopy for Investigations of the Characteristics of the Atmosphere of Mars (SPICAM) UV spectrometer on board the Mars Express spacecraft. The Vegard-Kaplan band system arises from the transition from the lowest N 2 triplet state (A 3 † + u ; v 0 ) to the electronic ground state (X 1 † + g ; v 00 ). It is populated by direct electron-impact excitation and by cascading from higher triplet states. The Venus UV dayglow is currently being probed by an instrument similar to SPICAM, the Spectroscopy for the Investigations of the Characteristics of the Atmosphere of Venus (SPICAV) UV spectrometer on Venus Express, but no N 2 emissions have been detected. Because the N 2 mixing ratios in the Venus thermosphere are larger than those in the thermosphere of Mars and the solar flux is greater at the orbit of Venus than that at Mars, we expect the Venus N 2 emissions to be significantly more intense than those of Mars. A prediction of the intensities of various N 2 emissions from Venus could be used to guide observations by the SPICAV and other instruments that are used to measure the Venus dayglow. Employing updated data, we here construct models of the low and high solar activity thermospheres of Venus, and we compute the integrated overhead intensities of 17 N 2 band systems and limb profiles of the Vegard-Kaplan bands. The ratios of the predicted intensities of the various N 2 bands at Venus to those at Mars are in the range 5.5-9.5.

show abstract

On the distribution of CO₂ and CO in the mesosphere and lower thermosphere

et al. 2014

View full text Add to dashboard Cite

We have used the Whole Atmosphere Community Climate Model (WACCM) to calculate the distribution of CO 2 and CO in the mesosphere and lower thermosphere (MLT), and we have compared the results with observations, mainly from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer and Michelson Interferometer for Passive Atmospheric Sounding satellite-borne instruments. We find that WACCM can reproduce the observed distribution of CO 2 in the MLT and the rapid falloff of CO 2 above about 80 km. Analysis of the principal terms in the calculated budget of CO 2 shows that its global-mean vertical profile is determined mainly by the competition between molecular diffusive separation and eddy mixing by gravity waves. The model underestimates somewhat the mixing ratio of CO 2 in the thermosphere compared to that in the observations, but we show that the discrepancy may be eliminated by a reasonable adjustment of the Prandtl number used to calculate the diffusivity due to gravity waves. Simulated CO is also consistent with observations, except that in the standard version of the model, its mixing ratio is uniformly lower than observed above about 100 km. We conclude that WACCM likely underestimates the rate of production of CO in the lower thermosphere from photolysis of CO 2 at wavelengths < 121 nm, and we show that this stems from the use of a very large absorption cross section for O 2 in the wavelength range 105-121 nm. When a smaller cross section is used, photolysis of CO 2 increases by a factor of 2-3 at~95-115 km and, as a result, CO mixing ratios become larger and agree much more closely with observations. We emphasize that the increase in CO 2 photolysis implies only minor changes in the vertical profile of CO 2 because photolytic loss is a minor term in the budget of CO 2 in the MLT.

show abstract

Ionization, luminosity, and heating of the upper atmosphere of Mars

Cited by 290 publications

References 118 publications

New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

Intensities of the Venusian N₂ electron‐impact excited dayglow emissions

On the distribution of CO₂ and CO in the mesosphere and lower thermosphere

Contact Info

Product

Resources

About

Ionization, luminosity, and heating of the upper atmosphere of Mars

Cited by 290 publications

References 118 publications

New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

Intensities of the Venusian N2 electron‐impact excited dayglow emissions

On the distribution of CO2 and CO in the mesosphere and lower thermosphere

Contact Info

Product

Resources

About

Intensities of the Venusian N₂ electron‐impact excited dayglow emissions

On the distribution of CO₂ and CO in the mesosphere and lower thermosphere