Photoabsorption in Ganymede’s atmosphere

Cessateur, Gaël; Lilensten, Jean; Barthélemy, Mathieu; Wit, T. Dudok de; Wedlund, Cyril Simon; Gronoff, Guillaume; Menager, H.; Kretzschmar, M.

doi:10.1016/j.icarus.2011.11.025

Cited by 5 publications

(13 citation statements)

References 53 publications

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“…Both emission measurements are of primary importance since the green to red lines ratio is commonly used for determining the abundances of CO and CO 2 relative to the H 2 O abundance in planetary and cometary atmospheres. Cessateur et al (2012a) have shown that emission from the deactivation of OH(A 2 R + ) to OH(X 2 P) is very small in the Thirupathaiah & Singh 2014). In this current paper, significant chemical reactions are considered in order to provide accurate dayglow emission estimates.…”

Section: Photodissociation and Photoexcitationmentioning

confidence: 99%

“…The total and partial photoabsorption cross-sections used throughout this study have been summarized by Cessateur et al (2012a).…”

Section: Atmospheric Response To Solar Uv Fluxmentioning

confidence: 99%

“…Some other loss processes should also be taken into account such as ion escape. However, Cessateur et al (2012a) have applied the same model to estimate the electron density within Ganymede's atmosphere. The fact that a good agreement with in-situ measurements performed by Galileo (Gurnett et al 1996) was found in that paper provides evidence for the validity of the applied methodological approach.…”

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confidence: 99%

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Photochemistry-emission coupled model for Europa and Ganymede

Cessateur

Barthélemy

Peinke

2016

J. Space Weather Space Clim.

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In the frame of the JUICE mission, preliminary studies of the Jupiter's icy moons, such as Ganymede and Europa, are mandatory. The present paper aims at characterizing the impact of the solar UV flux and its variability on their atmospheres. The solar UV radiation is responsible for the photoionization, photodissociation, and photoexcitation processes within planetary atmospheres. A 1-D photoabsorption model has been developed for different observational geometries, on the basis of a neutral atmospheric model. Considering various production and loss mechanisms but also the transport of oxygen atoms, we estimate the red and green line emissions from photo impact-induced excitation only. These dayglow emissions can represent few percent of the global airglow emission, mainly dominated by electron-induced excitation in auroral regions. For limb viewing conditions, red line emission is bright enough to be detected from actual spectrometers, from 338 R to 408 R according to the solar activity. This is also the case for the green line with 8 R at limb viewing. Considering a different neutral atmosphere model, with an O 2 column density 50% more important, leads to a 14% increase in the red line emissions for limb viewing close to the surface. This difference could be important enough to infer which neutral model is the most likely. However, uncertainties on the solar UV flux might also prevent to constrain the O 2 column density when using ground-based observations in the visible only. The impact of solar flares on the red line emissions for Europa has also been investigated within a planetary space weather context.

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Section: Photodissociation and Photoexcitationmentioning

confidence: 99%

“…The total and partial photoabsorption cross-sections used throughout this study have been summarized by Cessateur et al (2012a).…”

Section: Atmospheric Response To Solar Uv Fluxmentioning

confidence: 99%

mentioning

confidence: 99%

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Photochemistry-emission coupled model for Europa and Ganymede

Cessateur

Barthélemy

Peinke

2016

J. Space Weather Space Clim.

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“…The effects of the solar UV flux on Ganymede have recently been modeled by Cessateur et al (2012a). Production of different excited states of the atmospheric species has been calculated in various geometries at different latitudes as well as electron production.…”

Section: Example Using Ganymede: Study Of the Importance Of Specific mentioning

confidence: 99%

“…Moreover, this also shows that some solar proxies based on the integrated solar EUV flux cannot be used for assessing the solar variability in the EUV range. However, it is important to keep in mind that the uncertainties on the cross sections or on atmospheric models are often larger than 15% as mentioned in Cessateur et al (2012a). In parallel to these solar studies, much more effort needs to be spent clarifying these last points.…”

Section: Electron Productionmentioning

confidence: 99%

Sensitivity of upper atmospheric emissions calculations to solar/stellar UV flux

Barthélemy

Cessateur

2014

J. Space Weather Space Clim.

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The solar UV (UltraViolet) flux, especially the EUV (Extreme UltraViolet) and FUV (Far UltraViolet) components, is one of the main energetic inputs for planetary upper atmospheres. It drives various processes such as ionization, or dissociation which give rise to upper atmospheric emissions, especially in the UV and visible. These emissions are one of the main ways to investigate the upper atmospheres of planets. However, the uncertainties in the flux measurement or modeling can lead to biased estimates of fundamental atmospheric parameters, such as concentrations or temperatures in the atmospheres. We explore the various problems that can be identified regarding the uncertainties in solar/stellar UV flux by considering three examples. The worst case appears when the solar reflection component is dominant in the recorded spectrum as is seen for outer solar system measurements from HST (Hubble Space Telescope). We also show that the estimation of some particular line parameters (intensity and shape), especially Lyman a, is crucial, and that both total intensity and line profile are useful. In the case of exoplanets, the problem is quite critical since the UV flux of their parent stars is often very poorly known.

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Where does the Thermospheric Ionospheric GEospheric Research (TIGER) Program go?

Schmidtke

Avakyan

Berdermann

et al. 2015

Advances in Space Research

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International audienceAt the 10th Thermospheric Ionospheric GEospheric Research (TIGER/COSPAR) symposium held in Moscow in 2014 the achievements from the start of TIGER in 1998 were summarized. During that period, great progress was made in measuring, understanding, and modeling the highly variable UV-Soft X-ray (XUV) solar spectral irradiance (SSI), and its effects on the upper atmosphere. However, after more than 50 years of work the radiometric accuracy of SSI observation is still an issue and requires further improvement. Based on the extreme ultraviolet (EUV) data from the SOLAR/SolACES, and SDO/EVE instruments, we present a combined data set for the spectral range from 16.5 to 105.5 nm covering a period of 3.5 years from 2011 through mid of 2014. This data set is used in ionospheric modeling of the global total electron content (TEC), and in validating EUV SSI modeling. For further investigations the period of 3.5 years is being extended to about 12 years by including data from SOHO/SEM and TIMED/SEE instruments. Similarly, UV data are used in modeling activities. After summarizing the results, concepts are proposed for future real-time SSI measurements with in-flight calibration as experienced with the ISS SOLAR payload, for the development of a space weather camera for observing and investigating space weather phenomena in real-time, and for providing data sets for SSI and climate modeling. Other planned topics are the investigation of the relationship between solar EUV/UV and visible/near-infrared emissions, the impact of X-rays on the upper atmosphere, the development of solar EUV/UV indices for different applications, and establishing a shared TIGER data system for EUV/UV SSI data distribution and real-time streaming, also taking into account the achievements of the FP7 SOLID (First European SOLar Irradiance Data Exploitation) project. - For further progress it is imperative that coordinating activities in this special field of solar-terrestrial relations and solar physics is emphasized

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Photoabsorption in Ganymede’s atmosphere

Cited by 5 publications

References 53 publications

Photochemistry-emission coupled model for Europa and Ganymede

Photochemistry-emission coupled model for Europa and Ganymede

Sensitivity of upper atmospheric emissions calculations to solar/stellar UV flux

Where does the Thermospheric Ionospheric GEospheric Research (TIGER) Program go?

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