Solar irradiance reference spectra for two solar active levels

Thuillier, G.; Floyd, L.; Woods, Thomas N.; Cebula, R. P.; Hilsenrath, E.; Hersé, M.; Labs, D.

doi:10.1016/j.asr.2002.12.004

Cited by 121 publications

(121 citation statements)

References 25 publications

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“…Tarafdar & Vardya 1969). As UV spectrum for the host star HD 209458, we adopt the spectrum of the Sun (mean between minimum and maximum activity from Thuillier et al 2004) below 168 nm and a Kurucz synthetic spectrum 1 at longer wavelengths. For HD 189733b, below 335 nm we adopt a UV spectrum of Eridani based on the CAB X-exoplanets archive (Sanz-Forcada et al 2011) and observations with FUSE and HST (see details in Venot et al 2012), and a Kurucz synthetic spectrum 2 above 335 nm.…”

Section: Pseudo Two-dimensional Chemical Modelmentioning

confidence: 99%

Pseudo 2D chemical model of hot-Jupiter atmospheres: application to HD 209458b and HD 189733b

Agúndez

Parmentier

Venot

et al. 2014

A&A

139

265

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The high temperature contrast between the day and night sides of hot-Jupiter atmospheres may result in strong variations of the chemical composition with longitude if the atmosphere were at chemical equilibrium. On the other hand, the vigorous dynamics predicted in these atmospheres, with a strong equatorial jet, would tend to supress such longitudinal variations. To address this subject we have developed a pseudo two-dimensional model of a planetary atmosphere, which takes into account thermochemical kinetics, photochemistry, vertical mixing, and horizontal transport, the latter being modeled as a uniform zonal wind. We have applied the model to the atmospheres of the hot Jupiters HD 209458b and HD 189733b. The adopted eddy diffusion coefficients were calculated by following the behavior of passive tracers in three-dimensional general circulation models, which results in much lower eddy values than in previous estimates. We find that the distribution of molecules with altitude and longitude in the atmospheres of these two hot Jupiters is complex because of the interplay of the various physical and chemical processes at work. Much of the distribution of molecules is driven by the strong zonal wind and the limited extent of vertical transport, resulting in an important homogenization of the chemical composition with longitude. The homogenization is more marked in planets lacking a thermal inversion such as HD 189733b than in planets with a strong stratosphere such as HD 209458b. In general, molecular abundances are quenched horizontally to values typical of the hottest dayside regions, and thus the composition in the cooler nightside regions is highly contaminated by that of warmer dayside regions. As a consequence, the abundance of methane remains low, even below the predictions of previous one-dimensional models, which probably is in conflict with the high CH 4 content inferred from observations of the dayside of HD 209458b. Another consequence of the important longitudinal homogenization of the abundances is that the variability of the chemical composition has little effect on the way the emission spectrum is modified with phase and on the changes in the transmission spectrum from the transit ingress to the egress. These variations in the spectra are mainly due to changes in the temperature, rather than in the composition, between the different sides of the planet.

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Section: Pseudo Two-dimensional Chemical Modelmentioning

confidence: 99%

Pseudo 2D chemical model of hot-Jupiter atmospheres: application to HD 209458b and HD 189733b

Agúndez

Parmentier

Venot

et al. 2014

A&A

139

265

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“…To deal with this short exposure time, increasing the flux compared to the Sun to simulate longer irradiation times can of course be considered. The integrated solar flux between 100 and 300 nm is of the order of 2 × 10 13 ph cm −2 s −1 (Thuillier et al 2004b) while, in the same range of wavelengths, the flux generated by the DESIRS synchrotron source can reach 10 15 ph cm −2 s −1 , i.e. about 50 times more intense than from the Sun.…”

Section: Space Environment Versus Laboratory Environmentmentioning

confidence: 99%

“…in Earth's vicinity, the total solar irradiance (TSI) is equal to 1.361 kW m −2 (measured during the 2008 solar minimum period). This energetic input at the top of the atmosphere is made up of approximately 46% IR radiation, 46% visible light, and only 8% UV light (calculated from Thuillier et al 2004b (Fig. 2)).…”

Section: Photonsmentioning

confidence: 99%

Space as a Tool for Astrobiology: Review and Recommendations for Experimentations in Earth Orbit and Beyond

et al. 2017

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The space environment is regularly used for experiments addressing astrobiology research goals. The specific conditions prevailing in Earth orbit and beyond, notably the radiative environment (photons and energetic particles) and the possibility to conduct long-duration measurements, have been the main motivations for developing experimental concepts to expose chemical or biological samples to outer space, or to use the reentry of a spacecraft on Earth to simulate the fall of a meteorite. This paper represents an overview of past and current research in astrobiology conducted in Earth orbit and beyond, with a special focus on ESA missions such as Biopan, STONE (on Russian FOTON capsules) and EXPOSE facilities (outside the International Space Station). The future of exposure platforms is discussed, notably how they can be improved for better science return, and how to incorporate the use of small satellites such as those built in cubesat format.

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“…Figure 1 illustrates the spectral dependence of the full disk albedo of Titan from the mid-UV to the near-IR (McGrath et al 1998 for the UV, Karkoschka 1998 for the visual, Negrão et al 2006 for the near-IR) assuming Titan's optical radius varying with λ according to the Toon et al (1992) radius R T . The solar irradiance photon spectrum derived from Thuillier et al (2004) is given by the dashed line. The normalized instrument efficiencies in the different HST filters and the calculated spectral distribution of the registered photons are also indicated.…”

Section: Observationsmentioning

confidence: 99%

HST observations of the limb polarization of Titan

Bazzon

Schmid

Buenzli

2014

A&A

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Context. Titan is an excellent test case for detailed studies of the scattering polarization from thick hazy atmospheres. Accurate scattering and polarization parameters have been provided by the in situ measurements of the Cassini-Huygens landing probe. For Earth-bound observations Titan can only be observed at a backscattering situation, where the disk-integrated polarization is close to zero. However, with resolved imaging polarimetry a second order polarization signal along the entire limb of Titan can be measured. Aims. We present the first limb polarization measurements of Titan, which are compared as a test to our limb polarization models. Methods. Previously unpublished imaging polarimetry from the HST archive is presented, which resolves the disk of Titan. We determine flux-weighted averages of the limb polarization and radial limb polarization profiles, and investigate the degradation and cancelation effects in the polarization signal due to the limited spatial resolution of our observations. Taking this into account we derive corrected values for the limb polarization in Titan. The results are compared with limb polarization models, using atmosphere and haze scattering parameters from the literature. Results. In the wavelength bands between 250 nm and 2 μm a strong limb polarization of about 2−7% is detected with a position angle perpendicular to the limb. The fractional polarization is highest around 1 μm. As a first approximation, the polarization seems to be equally strong along the entire limb. The comparison of our data with model calculations and the literature shows that the detected polarization is compatible with expectations from previous polarimetric observations taken with Voyager 2, Pioneer 11, and the Huygens probe. Conclusions. Our results indicate that ground-based monitoring measurements of the limb-polarization of Titan could be useful for investigating local haze properties and the impact of short-term and seasonal variations of the hazy atmosphere of Titan. Planets with hazy atmospheres similar to Titan are particularly good candidates for detection with the polarimetric mode of the upcoming planet finder instrument at the VLT. Therefore, a good knowledge of the polarization properties of Titan is also important for the search and investigation of extra-solar planets.

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Solar irradiance reference spectra for two solar active levels

Cited by 121 publications

References 25 publications

Pseudo 2D chemical model of hot-Jupiter atmospheres: application to HD 209458b and HD 189733b

Pseudo 2D chemical model of hot-Jupiter atmospheres: application to HD 209458b and HD 189733b

Space as a Tool for Astrobiology: Review and Recommendations for Experimentations in Earth Orbit and Beyond

HST observations of the limb polarization of Titan

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