Negative ion densities in the ionosphere of Titan–Cassini RPWS/LP results

Shebanits, Oleg; Wahlund, Jan‐Erik; Mandt, K.; Ågren, Karin; Edberg, Niklas J. T.; Waite, J. H.

doi:10.1016/j.pss.2013.05.021

Cited by 78 publications

(105 citation statements)

References 27 publications

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“…In the considered altitude regime n e >n N (Shebanits et al, 2013) and in addition it is anticipated that α eff >> α MN (see Vigren et al, 2014). This implies that ion-electron recombination is the dominant plasma neutralization process in the considered altitude range.…”

Section: Flyby Information and Description Of Modelmentioning

confidence: 85%

“…The Cassini mission has revealed a chemically complex ionosphere around Titan. N 2 and CH 4 are ionized and/or dissociated by solar photons or particle irradiation marking the onset of a chain of chemical reactions, which produce hydrocarbon and nitrile ions, heavy positive and negative ions, and eventually aerosols (e.g., Vuitton et al, 2007;Waite et al, 2007;Wahlund et al, 2009;Crary et al, 2009;Ågren et al, 2012;Shebanits et al, 2013;Lavvas et al, 2013;Wellbrock et al, 2013). However, Titan dayside ionospheric models have shown difficulties in reproducing observed electron number densities (e.g., Vigren et al, 2013), as well as the observed number densities of HCNH + , the dominant ion in the main ionosphere (e.g., Vuitton et al, 2009;Westlake et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…A further difference in our model to derive plasma number densities is that we utilize the concept of an effective ionelectron recombination coefficient, which removes the computational burden of modeling in detail the complex chemistry associated with Titan's ionosphere. We use in the present study the most recently analyzed data from the INMS/CSN (Cui et al, 2012), INMS/OSI , CAPS/ELS (see e.g., Lewis et al, 2010;Wellbrock et al, 2012) and RPWS/LP (Edberg et al, 2013;Shebanits et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Ionization balance in Titan’s nightside ionosphere

Vigren

Galand

Yelle

et al. 2015

Icarus

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Ionization balance in Titan's nightside ionosphere, Icarus (2014), doi: http://dx.doi.org/10.1016/j.icarus. 2014.11.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ABSTRACTBased on a multi-instrumental Cassini dataset we make model versus observation comparisons of plasma number densities, n P =(n e n I ) 1/2 (n e and n I being the electron number density and total positive ion number density, respectively) and short-lived ion number densities (N + , CH 2 + , CH 3 + , CH 4 + ) in the southern hemisphere of Titan's nightside ionosphere over altitudes ranging from 1100 and 1200 km and from 1100 to 1350 km, respectively. The n P model assumes photochemical equilibrium, ionelectron pair production driven by magnetospheric electron precipitation and dissociative recombination as the principal plasma neutralization process. The model to derive short-lived-ion number densities assumes photochemical equilibrium for the short-lived ions, primary ion production by electron-impact ionization of N 2 and CH 4 and removal of the short-lived ions through reactions with CH 4 . It is shown that the models reasonably reproduce the observations, both with regards to n P and the number densities of the short-lived ions. This is contrasted by the difficulties in accurately reproducing ion and electron number densities in Titan's sunlit ionosphere.

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Section: Flyby Information and Description Of Modelmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ionization balance in Titan’s nightside ionosphere

Vigren

Galand

Yelle

et al. 2015

Icarus

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“…The ionosphere, peaking typically at altitudes of 1000-1100 km, is composed of hydrocarbon ions, nitrile ions, and other complex organic molecular ions, including ones being negatively charged, and is now known to be an important source region for Titanʼs organic aerosols (e.g., Coates et al 2007;Vuitton et al 2007;Waite et al 2007;Crary et al 2009;Wahlund et al 2009;Mandt et al 2012;Lavvas et al 2013;Wellbrock et al 2013;Shebanits et al 2013). The electron number density profile displays the basic variations anticipated from Chapman theory.…”

Section: Briefly On Titan's Ionosphere and Its Ionization Balancementioning

confidence: 96%

Suprathermal Electrons in Titan’s Sunlit Ionosphere: Model–observation Comparisons

Vigren

Galand

Wellbrock

et al. 2016

ApJ

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The dayside ionosphere of the Saturnian satellite Titan is generated mainly from photoionization of N 2 and CH 4 . We compare model-derived suprathermal electron intensities with spectra measured by the Cassini Plasma Spectrometer/Electron Spectrometer (CAPS/ELS) in Titanʼs sunlit ionosphere (altitudes of 970-1250 km) focusing on the T40, T41, T42, and T48 Titan flybys by the Cassini spacecraft. The model accounts only for photoelectrons and associated secondary electrons, with a main input being the impinging solar EUV spectra as measured by the Thermosphere Ionosphere Mesosphere Energy and Dynamics/Solar EUV Experiment and extrapolated to Saturn. Associated electron-impact electron production rates have been derived from ambient number densities of N 2 and CH 4 (measured by the Ion Neutral Mass Spectrometer/Closed Source Neutral mode) and related energy-dependent electron-impact ionization cross sections. When integrating up to electron energies of 60 eV, covering the bulk of the photoelectrons, the model-based values exceed the observationally based values typically by factors of ∼3 ± 1. This finding is possibly related to current difficulties in accurately reproducing the observed electron number densities in Titanʼs dayside ionosphere. We compare the utilized dayside CAPS/ELS spectra with ones measured in Titanʼs nightside ionosphere during the T55-T59 flybys. The investigated nightside locations were associated with higher fluxes of high-energy (>100 eV) electrons than the dayside locations. As expected, for similar neutral number densities, electrons with energies <60 eV give a higher relative contribution to the total electron-impact ionization rates on the dayside (due to the contribution from photoelectrons) than on the nightside.

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“…, and the plume of Enceladus 20,21 . It is also suggested through a detailed modeling t hat strong electron depletion can be found in comet's environment such as 67P/Churyumov-Gerasimenko, newly visited by Rosetta 16 have shown deep decline in electron number density and it is concluded that dust/aerosol-ion plasma 15 exists especially in the night side of the Titan. In case of Saturn's rings, the Cassini measurements during its mission (since 2004) have shown the existence of a decline in electron number density in E-ring and the plume of Enceladus…”

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confidence: 99%

Kinetic-Simulation Study of Propagation of Langmuir-Like Ionic Waves in Dusty Plasma

Hosseini-Jenab

Spanier

2017

IEEE Trans. Plasma Sci.

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The propagation of ionic perturbations in a dusty plasma is considered through a three-species kinetic simulation approach, in which the temporal evolution of all three elements i.e. electrons, ions and dust particles are followed based on the Vlasov equation coupled with the Poisson equation. Two cases are focused upon: firstly a fully electron depleted dusty plasma, i.e., a plasma consisting of ions and dust-particles. The second case includes dusty plasmas with large electron-to-ion temperature ratios. The main features of the ionic waves in these two settings including the dispersion relation and the Landau damping rate are studied. It is shown that the dispersion relation of the ionic waves perfectly matches the dispersion relation of Langmuir waves and hence are called Langmuirlike ionic waves and can be considered as Langmuir-like ionic waves. These waves can be theoretically predicted by the dispersion relation of the dust-ion-acoustic waves. The transition of ionic waves from dust-ion-acoustic to Langmuir-like waves are shown to be sharp/smooth in first/second case. The Landau damping rates based on simulation results are presented and compared with theoretical predictions wherever possible.

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Negative ion densities in the ionosphere of Titan–Cassini RPWS/LP results

Cited by 78 publications

References 27 publications

Ionization balance in Titan’s nightside ionosphere

Ionization balance in Titan’s nightside ionosphere

Suprathermal Electrons in Titan’s Sunlit Ionosphere: Model–observation Comparisons

Kinetic-Simulation Study of Propagation of Langmuir-Like Ionic Waves in Dusty Plasma

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