On the ionospheric structure of Titan

Ågren, Karin; Wahlund, Jan‐Erik; Garnier, Philippe; Modolo, Ronan; Cui, Jun; Galand, M.; Müller‐Wodarg, I. C. F.

doi:10.1016/j.pss.2009.04.012

Cited by 126 publications

(149 citation statements)

References 25 publications

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“…The dissociative recombination rate of HCNH + depends on the electron temperature. The Cassini Radio and Plasma Wave Science (RPWS/LP) measurements have reported an electronic temperature of 500 K (Ågren et al 2009;Galand et al 2010) over 950-1100 km. Such a value is surprisingly high, because electronic temperatures closer to the ∼150 K gas temperature are expected below ∼1050 km (Richards et al 2011).…”

Section: Discussionmentioning

confidence: 99%

First detection of hydrogen isocyanide (HNC) in Titan’s atmosphere

Moreno

Lellouch

Lara

et al. 2011

A&A

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We report on the first identification of hydrogen isocyanide (HNC) in Titan's atmosphere, from observations using the HIFI instrument on the Herschel Space Observatory. An emission line from the HNC J = 6 → 5 rotational transition at 543.897 GHz was measured in Titan on June 14 and December 31, 2010. Radiative transfer modeling indicates that the bulk of HNC is located above 400 km, with a column density in the range (0.6−1.5) × 10 13 cm −2 , but the observations cannot establish its vertical profile. In particular HNC could be restricted to the upper thermosphere (∼1000 km), in which case its local abundance relative to HCN could be as high as ∼0.3. HNC is probably formed mostly at ionospheric levels (950-1150 km) from dissociative recombination of HCNH + and possibly other heavier nitrile ions. Ionospheric loss of HNC occurs by protonation with XH + ions. Additional formation (e.g. from N( 4 S) + 3 CH 2 ) and loss routes (e.g. from isomerization to HCN) in the neutral atmosphere remain to be investigated.

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Section: Discussionmentioning

confidence: 99%

First detection of hydrogen isocyanide (HNC) in Titan’s atmosphere

Moreno

Lellouch

Lara

et al. 2011

A&A

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“…First, the major ionospheric ions are already molecular -i.e. HCNH + /C 2 H + 5 /CH + 5 (Cravens et al, 2006) -, so that their recombination rates with electrons are high and of the same order as for H 2 O + or H 3 O + (Anicich and McEwan, 1997). Moreover, given the time for the formation and the disappearing of artificial cavities, the Cassini spacecraft could neither detect them just after their creation nor during the next flyby.…”

Section: A Polar Plasma Cavitymentioning

confidence: 99%

“…Its dense molecular nitrogen atmosphere (Waite et al, 2005) is not protected by an intrinsic magnetic field, thus interacting directly with the Saturnian magnetosphere (Backes et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Titan's ionosphere in the magnetosheath: Cassini RPWS results during the T32 flyby

et al. 2009

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Abstract. The Cassini mission has provided much information about the Titan environment, with numerous low altitude encounters with the moon being always inside the magnetosphere. The only encounter taking place outside the magnetopause, in the magnetosheath, occurred the 13 June 2007 (T32 flyby). This paper is dedicated to the analysis of the Radio and Plasma Wave investigation data during this specific encounter, in particular with the Langmuir probe, providing a detailed picture of the cold plasma environment and of Titan's ionosphere with these unique plasma conditions. The various pressure terms were also calculated during the flyby. The comparison with the T30 flyby, whose geometry was very similar to the T32 encounter but where Titan was immersed in the kronian magnetosphere, reveals that the evolution of the incident plasma has a significant influence on the structure of the ionosphere, with in particular a change of the exo-ionospheric shape. The electrical conductivities are given along the trajectory of the spacecraft and the discovery of a polar plasma cavity is reported.

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“…Titan's photochemistry begins in the thermosphere/ionosphere with the photolytic destruction of N 2 and CH 4 . The dominant energy source and the primary driver of Titan's photochemistry is solar EUV/UV radiation (Ågren et al 2009;Sittler et al 2009;Lavvas et al 2011), although magnetospheric forcing may become more important at certain periods, as was shown to be the case during Cassini's prime mission Cui et al 2011;Westlake et al 2011).…”

Section: Introductionmentioning

confidence: 99%

The Role of Nitrogen in Titan’s Upper Atmospheric Hydrocarbon Chemistry Over the Solar Cycle

Luspay‐Kuti

Mandt

Westlake

et al. 2016

ApJ

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Titan's thermospheric photochemistry is primarily driven by solar radiation. Similarly to other planetary atmospheres, such as Mars', Titan's atmospheric structure is also directly affected by variations in the solar extreme-UV/UV output in response to the 11-year-long solar cycle. Here, we investigate the influence of nitrogen on the vertical production, loss, and abundance profiles of hydrocarbons as a function of the solar cycle. Our results show that changes in the atmospheric nitrogen atomic density (primarily in its ground state N( 4 S)) as a result of photon flux variations have important implications for the production of several minor hydrocarbons. The solar minimum enhancement of CH 3 , C 2 H 6 , and C 3 H 8 , despite the lower CH 4 photodissociation rates compared with solar maximum conditions, is explained by the role of N( 4 S). N( 4 S) indirectly controls the altitude of termolecular versus bimolecular chemical regimes through its relationship with CH 3 . When in higher abundance during solar maximum at lower altitudes, N( 4 S) increases the importance of bimolecular CH 3 + N( 4 S) reactions producing HCN and H 2 CN. The subsequent remarkable CH 3 loss and decrease in the CH 3 abundance at lower altitudes during solar maximum affects the overall hydrocarbon chemistry.

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On the ionospheric structure of Titan

Cited by 126 publications

References 25 publications

First detection of hydrogen isocyanide (HNC) in Titan’s atmosphere

First detection of hydrogen isocyanide (HNC) in Titan’s atmosphere

Titan's ionosphere in the magnetosheath: Cassini RPWS results during the T32 flyby

The Role of Nitrogen in Titan’s Upper Atmospheric Hydrocarbon Chemistry Over the Solar Cycle

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