On magnetospheric electron impact ionisation and dynamics in Titan's ram-side and polar ionosphere – a Cassini case study

Ågren, Karin; Wahlund, Jan‐Erik; Modolo, Ronan; Lummerzheim, D.; Galand, M.; Müller‐Wodarg, I. C. F.; Canu, P.; Kurth, W. S.; Cravens, T. E.; Yelle, R. V.; Waite, J. H.; Coates, A. J.; Lewis, G. R.; Young, D. T.; Bertucci, C.; Dougherty, M. K.

doi:10.5194/angeo-25-2359-2007

Cited by 83 publications

(103 citation statements)

References 33 publications

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“…Modelling activity by Agren et al (2007) showed that the night-time observation of a relatively dense ionosphere could be explained by the flux of magnetospheric electrons alone, although the observed intensity of these was higher than that needed to produce a good fit with RPWS LP ionosphere data.…”

Section: (B ) T5: Dark Ionospherementioning

confidence: 99%

Interaction of Titan's ionosphere with Saturn's magnetosphere

Coates

2008

Phil. Trans. R. Soc. A.

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Titan is the only Moon in the Solar System with a significant permanent atmosphere. Within this nitrogen-methane atmosphere, an ionosphere forms. Titan has no significant magnetic dipole moment, and is usually located inside Saturn's magnetosphere. Atmospheric particles are ionized both by sunlight and by particles from Saturn's magnetosphere, mainly electrons, which reach the top of the atmosphere. So far, the Cassini spacecraft has made over 45 close flybys of Titan, allowing measurements in the ionosphere and the surrounding magnetosphere under different conditions. Here we review how Titan's ionosphere and Saturn's magnetosphere interact, using measurements from Cassini low-energy particle detectors. In particular, we discuss ionization processes and ionospheric photoelectrons, including their effect on ion escape from the ionosphere. We also discuss one of the unexpected discoveries in Titan's ionosphere, the existence of extremely heavy negative ions up to 10 000 amu at 950 km altitude.

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Section: (B ) T5: Dark Ionospherementioning

confidence: 99%

Interaction of Titan's ionosphere with Saturn's magnetosphere

Coates

2008

Phil. Trans. R. Soc. A.

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“…The electron impact has been studied in Agren et al (2007), and re-analyzed in Cravens et al (2008Cravens et al ( , 2009, with an updated precipitation flux (used in this work). In order to fit the flux measurements at 1200 km with the model using a precipitation flux measured at 2730 km, the authors had to divide by 10 the input flux.…”

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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“…14 for several examples). Such a fact may significantly influence our understanding of the formation of nightside ions on Titan, which has been previously believed to be due to electron precipitation from Saturn's magnetosphere only (e.g., Cravens et al 2008aCravens et al , 2008bÅgren et al 2007). However, it appears from the Cassini observations that the transport of ions created at Titan's dayside may play an important role (Cui et al , 2010.…”

Section: Titan's Ionospheric Transport Processesmentioning

confidence: 98%

“…The energetic, hot electrons are from the external plasma in Saturn's magnetosphere passing Titan with a bulk speed of about 120 km/s. Their thermal velocity is much higher than the bulk speed (e.g., Coates et al 2007b;Ågren et al 2007;Cravens et al 2008a;. Both the bulk plasma flow and the high energy particle intensities in Saturn's magnetosphere, which the atmosphere of Titan experiences, varies with 2-3 orders of magnitude and is connected to the Saturn rotation period of about 10.7 hours (Bertucci et al 2009;Morooka et al 2009;Rymer et al 2009;Andrews et al 2010).…”

Section: Titan's Ionospheric Structurementioning

confidence: 98%

Recent Results from Titan’s Ionosphere

et al. 2011

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Titan has the most significant atmosphere of any moon in the solar system, with a pressure at the surface larger than the Earth's. It also has a significant ionosphere, which is usually immersed in Saturn's magnetosphere. Occasionally it exits into Saturn's magnetosheath. In this paper we review several recent advances in our understanding of Titan's ionosphere, and present some comparisons with the other unmagnetized objects Mars and Venus. We present aspects of the ionospheric structure, chemistry, electrodynamic coupling and transport processes. We also review observations of ionospheric photoelectrons at Titan, Mars and Venus. Where appropriate, we mention the effects on ionospheric escape.

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On magnetospheric electron impact ionisation and dynamics in Titan's ram-side and polar ionosphere – a Cassini case study

Cited by 83 publications

References 33 publications

Interaction of Titan's ionosphere with Saturn's magnetosphere

Interaction of Titan's ionosphere with Saturn's magnetosphere

Ionization processes in the atmosphere of Titan

Recent Results from Titan’s Ionosphere

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