Cosmic ray synthesis of organic molecules in Titan's atmosphere

Capone, L. A.; Dubach, J.; Whitten, R. C.; Prasad, S. S.; Santhanam, K.

doi:10.1016/0019-1035(80)90056-1

Cited by 52 publications

(35 citation statements)

References 37 publications

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“…The cosmic ray impact has been computed with a different technique by Molina-Cuberos et al (1999b), Capone et al (1976Capone et al ( , 1980, Borucki et al (1987Borucki et al ( , 2006, Borucki & Whitten (2008). Their approach solves a Boltzmann kinetic transport equation where the redistribution function is written such that the numbers of particles in the cascade are well reproduced (O'Brien 1969).…”

Section: Comparison With Other Modelsmentioning

confidence: 99%

Ionization processes in the atmosphere of Titan

Gronoff¹,

Lilensten²,

Desorgher

et al. 2009

A&A

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Context. The Cassini probe regularly passes in the vicinity of Titan, revealing new insights into particle precipitation thanks to the electron and proton spectrometer. Moreover, the Huygens probe has revealed an ionized layer at 65 km induced by cosmic rays. The impact of these different particles on the chemistry of Titan is probably very strong. Aims. In this article, we compute the whole ionization in the atmosphere of Titan: from the cosmic rays near the ground to the EUV in the upper atmosphere. The meteoritic layer is not taken into account. Methods. We used the transTitan model to compute the electron and EUV impact, and the planetocosmics code to compute the influence of protons and oxygen ions. We coupled the two models to study the influence of the secondary electrons obtained by planetocosmics through the transTitan code. The resulting model improves the accuracy of the calculation through the transport of electrons in the atmosphere. Results. The whole ionization is computed and studied in details. During the day, the cosmic ray ionization peak is as strong as the UV-EUV one. Electrons and protons are very important depending the precipitation conditions. Protons can create a layer at 500 km, while electrons tend to ionize near 800 km. The oxygen ion impact is near 900 km. The results shows few differences to precedent models for the nightside T5 fly-by of Cassini, and can highlight the sources of the different ion layers detected by radio measurements. Conclusions. The new model successfully computes the ion production in the atmosphere of Titan. For the first time, a full electron and ion profile has been computed from 0 to 1600 km, which compares qualitatively with measurements. This result can be used by chemical models.

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Section: Comparison With Other Modelsmentioning

confidence: 99%

Ionization processes in the atmosphere of Titan

Gronoff¹,

Lilensten²,

Desorgher

et al. 2009

A&A

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“…They calculated a negative to positive ion ratio of ~10 -4 in the nighttime ionosphere, which became approximately four orders of magnitude lower in the daytime ionosphere because of the high photo-detachment rate. A decade later, Borucki et al (1987) considered the possible formation of negative ions by three-body electron attachment to radicals such as NH 2 , CH 3 , CN, C 2 H, and H. While CN and C 2 H form relatively stable negative ions (see section 3.1), the concentrations of these radicals, as calculated by Capone et al (1980) and Yung et al (1984), are too small for them to be a significant source of negative ions. Calculated equilibrium concentrations of CH 3 , NH 2 , and H are larger, but the negative ions they form are far less stable against photo-detachment (see section 3.1).…”

Section: Introductionmentioning

confidence: 99%

Negative ion chemistry in Titan's upper atmosphere

Vuitton

Lavvas

Yelle

et al. 2009

Planetary and Space Science

257

255

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“…One of the important input for the chemical models is the ionization by Galactic cosmic rays (GCR) (Lavvas et al 2008). The first computation of cosmic ray ionization in the atmosphere of Titan was addressed by Capone et al (1976Capone et al ( , 1980Capone et al ( , 1983 (with an improvement following the discovery of N 2 in the Titan's atmosphere). The study of GCR in the atmosphere of Titan was also performed by Borucki et al (1987); Molina-Cuberos et al (1999a); Molina-Cuberos et al (1999b); Wilson & Atreya (2005); Borucki et al (2006); Borucki & Whitten (2008), and Krasnopolsky (2009Krasnopolsky ( , 2010, all of these ionization computations being based on the same model from O'Brien (1969).…”

Section: Introductionmentioning

confidence: 99%

Ionization processes in the atmosphere of Titan

Gronoff

Mertens

Lilensten

et al. 2011

A&A

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Context. The Cassini-Huygens mission has revealed the importance of particle precipitation in the atmosphere of Titan thanks to in-situ measurements. These ionizing particles (electrons, protons, and cosmic rays) have a strong impact on the chemistry, hence must be modeled. Aims. We revisit our computation of ionization in the atmosphere of Titan by cosmic rays. The high-energy high-mass ions are taken into account to improve the precision of the calculation of the ion production profile. Methods. The Badhwahr and O'Neill model for cosmic ray spectrum was adapted for the Titan model. We used the TransTitan model coupled with the Planetocosmics model to compute the ion production by cosmic rays. We compared the results with the NAIRAS/HZETRN ionization model used for the first time for a body that differs from the Earth. Results. The cosmic ray ionization is computed for five groups of cosmic rays, depending on their charge and mass: protons, alpha, Z = 8 (oxygen), Z = 14 (silicon), and Z = 26 (iron) nucleus. Protons and alpha particles ionize mainly at 65 km altitude, while the higher mass nucleons ionize at higher altitudes. Nevertheless, the ionization at higher altitude is insufficient to obscure the impact of Saturn's magnetosphere protons at a 500 km altitude. The ionization rate at the peak (altitude: 65 km, for all the different conditions) lies between 30 and 40 cm −3 s −1 . Conclusions. These new computations show for the first time the importance of high Z cosmic rays on the ionization of the Titan atmosphere. The updated full ionization profile shape does not differ significantly from that found in our previous calculations (Paper I: Gronoff et al. 2009, 506, 955) but undergoes a strong increase in intensity below an altitude of 400 km, especially between 200 and 400 km altitude where alpha and heavier particles (in the cosmic ray spectrum) are responsible for 40% of the ionization. The comparison of several models of ionization and cosmic ray spectra (in intensity and composition) reassures us about the stability of the altitude of the ionization peak (65 km altitude) with respect to the solar activity.

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Cosmic ray synthesis of organic molecules in Titan's atmosphere

Cited by 52 publications

References 37 publications

Ionization processes in the atmosphere of Titan

Ionization processes in the atmosphere of Titan

Negative ion chemistry in Titan's upper atmosphere

Ionization processes in the atmosphere of Titan

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