Recent Results from Titan’s Ionosphere

Coates, A. J.; Wahlund, Jan‐Erik; Ågren, Karin; Edberg, Niklas J. T.; Cui, Jun; Wellbrock, A.; Szegö, K.

doi:10.1007/s11214-011-9826-4

Cited by 15 publications

(10 citation statements)

References 120 publications

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“…[49] We note again that photoelectrons observed in the tail are sensitive tracers of a magnetic connection to the dayside ionosphere, and are consistent with the observed field direction [Wei et al, 2011] for all the encounters reported here (T9, T75, T63) [cf. Coates et al, 2007Coates et al, , 2011aCoates et al, , 2011bWellbrock et al, 2012]. Additional observations during other tail photoelectron intervals at Titan encounters T40, T17, T15 are reported by Wellbrock et al, 2012. [50] Acknowledgments.…”

Section: Discussionmentioning

confidence: 74%

“…[2] Cassini has revealed many important aspects of Titan's ionosphere (e.g., reviews by Cravens et al [2009] and Coates et al [2011a]). Titan, orbiting at 20 Saturn radii (R s ) from Saturn, spends most of its time in Saturn's magnetosphere, and recent papers have documented the variety of upstream conditions at Titan's orbit [Rymer et al, 2009Arridge et al, 2011a.…”

Section: Introductionmentioning

confidence: 99%

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Cassini in Titan's tail: CAPS observations of plasma escape

et al. 2012

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[1] We present observations of CAPS electron and ion spectra during Titan distant tail crossings at 5,000-10,000 km altitude by the Cassini spacecraft. In common with closer tail encounters, we identify ionospheric plasma in the tail. Some of the electron spectra indicate a direct magnetic connection to Titan's dayside ionosphere due to the presence of ionospheric photoelectrons. Ion observations reveal heavy (m/q$ 16 and 28) and light (m/q = 1-2) ion populations streaming into the tail. Using the distant tail encounters T9, T75 and T63, we estimate total plasma loss rates from Titan via this process of (4.2, 0.96 and 2.3) Â 10 24 ions s À1 respectively for the three encounters, values which are in agreement with some simulations but slightly lower than earlier estimates based on nondifferential techniques. Using the mass-separated data, this corresponds to mass loss rates of (8.9, 1.6, 4.0) Â 10 25 amu s À1 for T9, T75 and T63 respectively, an average loss rate of $7 tonnes per Earth day. Remarkably, all of the tail encounters studied here indicate a split tail feature, indicating that this may be a common feature in Titan's interaction with Saturn's magnetosphere.

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Section: Discussionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Cassini in Titan's tail: CAPS observations of plasma escape

et al. 2012

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“…On the other hand, Wellbrock et al (2009), A. Wellbrock (2021, in preparation) and Coates et al (2009Coates et al ( , 2011 show that heavy anion densities under illuminated conditions past the terminator are lower than unilluminated conditions in the deeper nightside ionosphere, as observed during flybys such as T57. The higher densities of heavy anions in unilluminated conditions could provide a competing pathway to heavy cation production.…”

Section: Variations Between Flybysmentioning

confidence: 97%

Heavy positive ion groups in Titan's ionosphere: Cassini Plasma Spectrometer IBS observations

Haythornthwaite

Coates

Jones

et al. 2024

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Titan's ionosphere contains a plethora of hydrocarbons and nitrile cations and anions as measured by the Ion Neutral Mass Spectrometer and Cassini Plasma Spectrometer (CAPS) on board the Cassini spacecraft. Data from the CAPS Ion Beam Spectrometer (IBS) sensor have been examined for five close encounters of Titan during 2009. The high relative velocity of Cassini with respect to the cold ions in Titan's ionosphere allows CAPS IBS to function as a mass spectrometer. Positive ion masses between 170 and 310 u/q are examined with ion mass groups identified between 170 and 275 u/q containing between 14 and 21 heavy (carbon/nitrogen/oxygen) atoms. These groups are the heaviest positive ion groups reported so far from the available in situ ion data at Titan. The ion group peaks are found to be consistent with masses associated with polycyclic aromatic compounds (PAC), including polycyclic aromatic hydrocarbon (PAH) and nitrogen-bearing polycyclic aromatic molecular ions. The ion group peak identifications are compared with previously proposed neutral PAHs and are found to be at similar masses, supporting a PAH interpretation. The spacing between the ion group peaks is also investigated, finding a spacing of 12 or 13 u/q indicating the addition of C or CH. Lastly, the occurrence of several ion groups is seen to vary across the five flybys studied, possibly relating to the varying solar radiation conditions observed across the flybys. These findings further the understanding between the low-mass ions and the high-mass negative ions, as well as with aerosol formation in Titan's atmosphere.

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“…Wellbrock 2021, in preparation). On the other hand, Wellbrock et al (2009), A. Wellbrock (2021, in preparation) and Coates et al (2009Coates et al ( , 2011 show that heavy anion densities under illuminated conditions past the terminator are lower than unilluminated conditions in the deeper nightside ionosphere, as observed during flybys such as T57. The higher densities of heavy anions in unilluminated conditions could provide a competing pathway to heavy cation production.…”

Section: Variations Between Flybysmentioning

confidence: 97%

“…Due to Titan's extended atmosphere the effects of solar EUV radiation on ions are seen past the terminator, up to SZA values of 135°at 1000 km (Ågren et al 2009;Coates et al 2009Coates et al , 2011Wellbrock et al 2009Wellbrock et al , 2013A. Wellbrock 2021, in preparation), although at high SZA values the solar radiation is attenuated by passing through more of Titan's atmosphere studied the diurnal variations of positive ions, finding that light ions were strongly depleted on the nightside while the heavy ions were moderately depleted and the most significant diurnal variations were seen at low altitudes.…”

Section: Variations Between Flybysmentioning

confidence: 99%

Heavy positive ion groups in Titan's ionosphere: Cassini Plasma Spectrometer IBS observations

Haythornthwaite

Coates

Jones

et al. 2021

Preprint

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IntroductionTitan is the largest moon of Saturn and has a thick extended atmosphere along with a large ionosphere. Titan's ionosphere contains a plethora of hydrocarbons and nitrile cations and anions as measured by the Ion Neutral Mass Spectrometer and Cassini Plasma Spectrometer (CAPS) onboard the Cassini spacecraft1.Previous ion composition studies in Titan&#8217;s ionosphere by Cassini instruments revealed "families" of ions around particular mass values and a regular spacing of 12 to 14 u/q between mass groups 2. These are thought to be related to a carbon or nitrogen backbone that dominates the ion chemistry2. Previous studies also identified possible heavy ions such as naphthalene, anthracene derivatives and an anthracene dimer at 130, 170 and 335 u/q respectively1.&#160;&#160;Methodology&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; The CAPS Ion Beam Spectrometer3 is an electrostatic analyser that measures energy/charge ratios of ions. During the Titan flybys Cassini had a high velocity (~6 km/s) relative to the low ion velocities (< 230 m/s) observed in the ionosphere. The ions were also cold, having ion temperatures around 150K. The combination of these factors meant that the ions appeared as a highly-directed supersonic beam in the spacecraft frame. This means the ions appear at kinetic energies associated with the spacecraft velocity and the ion mass, therefore the measured energy spectra (eV/q) can be converted to mass spectra (u/q).&#160;Results and ConclusionsPositive ion masses between 170 and 310 u/q are examined with ion mass groups identified between 170 and 275 u/q containing between 14 and 21 heavy (carbon/nitrogen/oxygen) atoms4. These groups are the heaviest positive ion groups reported so far from the available in situ ion data at Titan.The ion group peaks are found to be consistent with masses associated with Polycyclic Aromatic Compounds, including Polycyclic Aromatic Hydrocarbon (PAH) and nitrogen-bearing polycyclic aromatic molecular ions. The ion group peak identifications are compared with previously proposed neutral PAHs5 and are found to be at similar masses, supporting a PAH interpretation. The spacing between the ion group peaks is also investigated, finding a spacing of 12 or 13 u/q indicating the addition of C or CH. Lastly, the occurrence of several ion groups is seen to vary across the five flybys studied, possibly relating to the varying solar radiation conditions observed across the flybys.The discovery of these groups will aid future atmospheric chemical models of Titan through identification of prominent heavy positive ions and further the understanding between the low mass ions and the high mass negative ions, as well as the process of aerosol formation in Titan's atmosphere.References1. Waite et al., The Process of Tholin Formation in Titan&#8217;s Upper Atmosphere, Sci., 2007, doi:10.1126/science.11397272. Crary et al., Heavy ions, temperatures and winds in Titan's ionosphere: Combined Cassini CAPS and INMS observations, P&SS, 2009, doi:10.1016/j.pss.2009.09.006.3. Young et al., Cassini Plasma Spectrometer Investigation. Space Sci. Rev., 2004, doi:10.1007/s11214-004-1406-44. Haythornthwaite et al., Heavy Positive Ion Groups in Titan's Ionosphere from Cassini Plasma Spectrometer IBS Observations, eprint arXiv:2009.087495. L&#243;pez-Puertas et al., Large Abundances of Polycyclic Aromatic Hydrocarbons in Titan's Upper Atmosphere, ApJ, 2013, doi:10.1088/0004-637X/770/2/132

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Recent Results from Titan’s Ionosphere

Cited by 15 publications

References 120 publications

Cassini in Titan's tail: CAPS observations of plasma escape

Cassini in Titan's tail: CAPS observations of plasma escape

Heavy positive ion groups in Titan's ionosphere: Cassini Plasma Spectrometer IBS observations

Heavy positive ion groups in Titan's ionosphere: Cassini Plasma Spectrometer IBS observations

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