Airglow remote sensing of the seasonal variation of the Martian upper atmosphere: MAVEN limb observations and model comparison

Gkouvelis, Leonardos; Gérard, Jean‐Claude; Ritter, Birgit; Hubert, Benoît; Schneider, Nicholas M.; Jain, Sonal

doi:10.1016/j.icarus.2020.113666

Cited by 13 publications

(23 citation statements)

References 29 publications

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“…A comparison of the UVIS 297.2 nm observations with those from IUVS-MAVEN 15,18 provides indirect further confirmation of the detection of the green line. Simultaneous and co-located observations from MAVEN were not possible as the periapsis of MAVEN was on the nightside during the period of the TGO limb observations.…”

Section: Lettersmentioning

confidence: 64%

“…Its altitude is a proxy of the location of the 0.39 μbar level, if the small variation of the gravity in the mesosphere is neglected and a constant mean molecular mass in the overhead atmospheric column is assumed. Monitoring of the changes of the lower emission peak makes it a powerful tool for remotely identifying altitude variations of the pressure level in the mesosphere with latitude, season and atmospheric dust load 15,18 .…”

Section: Lettersmentioning

confidence: 99%

“…The MCD CO 2 density has been scaled down by a factor of 0.5 (ref. 18 ). The solar flux is provided by the synthetic spectra with a 1 nm resolution normalized to the three-channel measurements of the EUV monitor (EUVM) on board MAVEN 21 .…”

Section: Nature Astronomymentioning

confidence: 99%

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Detection of green line emission in the dayside atmosphere of Mars from NOMAD-TGO observations

et al. 2020

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The oxygen emission at 557.7 nm is a ubiquitous component of the spectrum of the terrestrial polar aurora and the reason for its usual green colour 1 . It is also observed as a thin layer of glow surrounding the Earth near 90 km altitude in the dayside atmosphere 2,3 but it has so far eluded detection in other planets. Here we report dayglow observations of the green line outside the Earth. They have been performed with the Nadir and Occultation for Mars Discovery ultraviolet and visible spectrometer instrument on board the European Space Agency's ExoMars Trace Gas Orbiter. Using a special observation mode, scans of the dayside limb provide the altitude distribution of the intensity of the 557.7 nm line and its variability. Two intensity peaks are observed near 80 and 120 km altitude, corresponding to photodissociation of CO 2 by solar Lyman α and extreme ultraviolet radiation, respectively. A weaker emission, originating from the same upper level of the oxygen atom, is observed in the near ultraviolet at 297.2 nm. These simultaneous measurements of both oxygen lines make it possible to directly derive a ratio of 16.5 between the visible and ultraviolet emissions, and thereby clarify a controversy between discordant ab initio calculations and atmospheric measurements that has persisted despite multiple efforts. This ratio is considered a standard for measurements connecting the ultraviolet and visible spectral regions. This result has consequences for the study of auroral and airglow processes and for spectral calibration.The presence of the Martian green line dayglow emission was predicted about 40 years ago 4 . However, observations dedicated to the Martian dayglow have so far been sensitive to radiation beyond 340 nm, and thus focused on the ultraviolet (UV) spectrum [5][6][7][8] , including the Oi 297.2 nm emission. The [Oi] 557.7 and 297.2 nm forbidden emissions have the same 1 S upper state, so their intensity ratio is equal to that of their transition probability. The two transition probabilities and their ratio R = I(557.7 nm)/I(297.2 nm) have been obtained from ab initio calculations. The value recommended by NIST 1 is R = 16.7. However, atmospheric observations of the two emissions have led to lower values: R = 9.8 ± 1.0 in the terrestrial nightglow 9 and 9.3 ± 0.5 in the aurora 10 . These values depend on the instrumental calibration of two spectral windows bridged with the O 2 Herzberg i transition. As this ratio is invariant at low pressure, it is a useful standard for measurements connecting the UV and the visible regions.

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Section: Lettersmentioning

confidence: 64%

Section: Lettersmentioning

confidence: 99%

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Detection of green line emission in the dayside atmosphere of Mars from NOMAD-TGO observations

et al. 2020

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“…The method to describe the seasonal variations of the isobar was described by Gkouvelis et al (2020). It is based on the specificity that the O( 1 S) level is solely excited by photodissociation of CO 2 by solar Lyman radiation.…”

Section: Measurements Of the 2972 Nm Dayglow Emissionmentioning

confidence: 99%

“…altitude of the OI 297.2 nm dayglow showed that the altitude typically rises from about 80 km up to more than 90 km between Ls = 185°and 270° (Gkouvelis et al, 2020).…”

Section: 1029/2020gl087468mentioning

confidence: 99%

Isobar Altitude Variations in the Upper Mesosphere Observed With IUVS‐MAVEN in Response to Martian Dust Storms

Gkouvelis

Gérard

González‐Galindo

et al. 2020

Geophysical Research Letters

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We report limb measurements of the oxygen dayglow emission at 297.2 nm performed during four Martian dust storms. The emission peak provides a good remote sensing tool to probe changes of the altitude of the 39 mPa pressure level for the first time during dust storms. We illustrate the time variation of these changes and compare them with the infrared opacity in the lower atmosphere. We find that the 39 mPa level rises in response to the increase in dust opacity. It reaches a plateau, and additional dust load does not significantly increase its altitude. Numerical simulations with the LMD global circulation model shows a similar response, except for the event observed during MY33 regional storm when the model fails to reproduce the observed variations. Observations collected during the onset of the global dust storm in June 2018 show that the upper atmosphere rapidly responds within two Martian days to the increased amount of tropospheric dust. Plain Language Summary Earlier studies have shown that the oxygen dayglow emission at 297.2 nm is a good tracer of the response of the upper atmosphere to atmospheric perturbations such as dust storms. In this work, we use MAVEN-IUVS observations during four different dust storm episodes in order to follow their influence on the atmospheric structure. We combine these measurements with concurrent observations of the dust load in the lower atmosphere monitored by infrared absorption. We find that the atmospheric layers move up as the atmospheric dust load increases. However, we show that there is a saturation effect limiting the rise of the layers at a given dust content. High time resolution observations performed during the first phase of the 2018 global dust storm indicate that the upper atmosphere responds quite fast following the onset of the storm.

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Energy balance and heating mechanisms of the Martian Upper atmosphere with the NASA Ames MGCM.

Gkouvelis

Brecht

Kling

et al. 2021

Preprint

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Airglow remote sensing of the seasonal variation of the Martian upper atmosphere: MAVEN limb observations and model comparison

Cited by 13 publications

References 29 publications

Detection of green line emission in the dayside atmosphere of Mars from NOMAD-TGO observations

Detection of green line emission in the dayside atmosphere of Mars from NOMAD-TGO observations

Isobar Altitude Variations in the Upper Mesosphere Observed With IUVS‐MAVEN in Response to Martian Dust Storms

Energy balance and heating mechanisms of the Martian Upper atmosphere with the NASA Ames MGCM.

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