The orientation of Titan’s dayside ionosphere and its effects on Titan’s plasma interaction

Ledvina, S. A.; Brecht, S. H.; Cravens, T. E.

doi:10.5047/eps.2011.08.009

Cited by 21 publications

(23 citation statements)

References 67 publications

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“…Titan's chemically complex ionosphere is also quite dynamic and can be driven by magnetospheric pressure, thermal pressure, and thermospheric neutral winds [ Ledvina and Cravens, ; Cravens et al ., ; Bell et al ., ; Ma et al ., ]. A combination of forces can lead to transport of ionospheric parcels, and this can sometimes cause ionospheric densities, even on the dayside, to deviate from equilibrium state densities [ Cui et al ., ; Cravens et al ., ; Ledvina et al ., ]. Cui et al [] studied ion transport in Titan's ionosphere by using electron distribution data from nine close encounters of the Cassini spacecraft with Titan (TA‐T40) and comparing them with the diffusive equilibrium model results.…”

Section: Data‐model Comparisonsmentioning

confidence: 99%

Solar cycle variations in ion composition in the dayside ionosphere of Titan

et al. 2016

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One Titanian year spans over two complete solar cycles, and the solar irradiance has a significant effect on ionospheric densities. Solar cycle 24 has been one of the quietest cycles on record. In this paper we show data from the Cassini ion and neutral mass spectrometer (INMS) and the radio and plasma wave science Langmuir probe spanning the time period from early 2005, at the declining phase of solar cycle 23, to late 2015 at the declining phase of solar cycle 24. Densities of different ion species measured by the INMS show a consistent enhancement for high solar activity, particularly near the ionospheric peak. The density enhancement is best seen in primary ion species such as CH3+ rather than heavier ion species such as HCNH+. Unlike at Earth, where the ionosphere and atmosphere thermally expand at high solar activity, at Titan the altitude of the ionospheric peak decreases, indicating that the underlying neutral atmosphere was less extensive. Among the major ion species, CH5+ shows the largest decrease in peak altitude, whereas heavy ions such as C3H5+ show very little decrease. We also calculate the ion production rates using a theoretical model and a simple empirical model using INMS data and show that these effectively predict the increased ion production rates at high solar activity.

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Section: Data‐model Comparisonsmentioning

confidence: 99%

Solar cycle variations in ion composition in the dayside ionosphere of Titan

et al. 2016

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“…[]. In situ magnetic field measurements [e.g., Neubauer et al ., ; Bertucci et al ., ] combined with post‐Cassini global MHD and hybrid models [ Ma et al ., ; Ledvina et al ., ] demonstrated that the magnetic field line topology is complex, particularly at lower altitudes. The magnetic fields produced by global models do not generally agree with magnetometer data below 1300 km or so [ Ulusen et al ., ].…”

Section: Introductionmentioning

confidence: 99%

An empirical approach to modeling ion production rates in Titan's ionosphere II: Ion production rates on the nightside

et al. 2015

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Ionization of neutrals by precipitating electrons and ions is the main source of Titan's nightside ionosphere. This paper has two goals: (1) characterization of the role of electron impact ionization on the nightside ionosphere for different magnetospheric conditions and (2) presentation of empirical ion production rates determined using densities measured by the Cassini Ion and Neutral Mass Spectrometer on the nightside. The ionosphere between 1000 and 1400 km is emphasized. We adopt electron fluxes measured by the Cassini Plasma Spectrometer-Electron Spectrometer and the Magnetospheric Imaging Instrument as classified by Rymer et al. (2009). The current paper follows an earlier paper (Paper I), in which we investigated sources of Titan's dayside ionosphere and demonstrated that the photoionization process is well understood. The current paper (Paper II) demonstrates that modeled and empirical ionization rates on the nightside are in agreement with an electron precipitation source above 1100 km. Ion production rate profiles appropriate for different Saturnian magnetospheric conditions, as outlined by Rymer et al., are constructed for various magnetic field topologies. Empirical production rate profiles are generated for deep nightside flybys of Titan. The results also suggest that at lower altitudes (below 1100 km) another source, such as ion precipitation, is probably needed.

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“…Several hybrid and MHD models have been produced to explain both observations of ionospheric plasma in Titan's more distant tail [cf. Keller and Cravens , 1994; Snowden et al , 2007; Modolo et al , 2007; Ma et al , 2007; Simon et al , 2007; Sillanpää et al , 2007; Lipatov et al , 2011; Ledvina et al , 2012] and the existence of fossil fields below Titan's exobase [cf. Ma et al , 2009; Simon et al , 2009].…”

Section: Introductionmentioning

confidence: 99%

The observed composition of ions outflowing from Titan

Westlake¹,

Paranicas²,

Cravens³

et al. 2012

Geophysical Research Letters

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[1] We report on Cassini Ion and Neutral Mass Spectrometer (INMS) observations above Titan's exobase at altitudes of 2225 km to 3034 km. We observe significant densities of CH 5 + , HCNH + and C 2 H 5 + that require ion-molecule reactions to be produced in the quantities observed. The measured composition and ion velocity (about 0.8-1.5 km/s) suggest that the observed ions must have been created deep inside Titan's ionosphere (below the exobase) and then transported to the detection altitude. Plasma motion from below Titan's exobase to large distances can be driven by a combination of thermal pressure and magnetic forces. The observed outward flows may link the main ionosphere with the more distant wake and provide a source of hydrocarbon ions in the Saturnian system.

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The orientation of Titan’s dayside ionosphere and its effects on Titan’s plasma interaction

Cited by 21 publications

References 67 publications

Solar cycle variations in ion composition in the dayside ionosphere of Titan

Solar cycle variations in ion composition in the dayside ionosphere of Titan

An empirical approach to modeling ion production rates in Titan's ionosphere II: Ion production rates on the nightside

The observed composition of ions outflowing from Titan

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