Search Publications
Negative ion chemistry in Titan's upper atmosphere
Lewis, G. R.; Coates, A. J.; Wahlund, J. -E. +5 more
The Electron Spectrometer (ELS), one of the sensors making up the Cassini Plasma Spectrometer (CAPS) revealed the existence of numerous negative ions in Titan's upper atmosphere. The observations at closest approach (∼1000 km) show evidence for negatively charged ions up to ∼10,000 amu/q, as well as two distinct peaks at 22±4 and 44±8 amu/q, and m…
INMS-derived composition of Titan's upper atmosphere: Analysis methods and model comparison
Mandt, Kathleen E.; Waite, J. Hunter; Magee, Brian A. +3 more
The Cassini Ion and Neutral Mass Spectrometer (INMS) has recorded full altitude profile data from 20 low-altitude Titan encounters during the nominal mission (July 2004-2008). These encounters were TA, T5, T16, T18, T19, T21, T23, T25, T26, T28, T29, T30, T32, T36, T37, T39, T40, T41, T42, and T43. In this work we present an analysis of the data o…
Recurrent energization of plasma in the midnight-to-dawn quadrant of Saturn's magnetosphere, and its relationship to auroral UV and radio emissions
Gurnett, D. A.; Dougherty, M. K.; Krimigis, S. M. +11 more
We demonstrate that under some magnetospheric conditions protons and oxygen ions are accelerated once per Saturn magnetosphere rotation, at a preferred local time between midnight and dawn. Although enhancements in energetic neutral atom (ENA) emission may in general occur at any local time and at any time in a Saturn rotation, those enhancements …
Detection of dusty plasma near the E-ring of Saturn
Gurnett, D. A.; Hospodarsky, G. B.; Kurth, W. S. +12 more
We present several independent in-situ measurements, which provide evidence that charged dust in the E-ring interacts collectively with the dense surrounding plasma disk of Saturn, i.e., form a system of dust-plasma interaction. The results are based on data sampled by the Radio and Plasma Wave Science (RPWS) investigation onboard Cassini, which a…
Heavy ions, temperatures and winds in Titan's ionosphere: Combined Cassini CAPS and INMS observations
Young, D. T.; Waite, J. H.; Magee, B. A. +3 more
Multiple Titan encounters by the Cassini spacecraft have shown that ion chemistry in Titan's upper atmosphere is much more complex than previously thought. As well as showing a great variety of species present below 100 amu, they also include the detection of negative ions and of large abundances of ions above 100 amu. Here, we use data from two C…
On the ionospheric structure of Titan
Garnier, P.; Wahlund, J. -E.; Ågren, K. +4 more
In this study we present data from 17 Titan flybys showing that solar photons are the main ionisation source of Titan's dayside atmosphere. This is the first comprehensive study of Solar Zenith Angle (SZA) dependence of the electron number density and electron temperature at the ionospheric peak. The results show on average four times more plasma …
Heavy negative ions in Titan's ionosphere: Altitude and latitude dependence
Lewis, G. R.; Coates, A. J.; Jones, G. H. +4 more
One of the unexpected results of the Cassini mission was the discovery of negative ions at altitudes between 950 and 1400 km in Titan's ionosphere with masses up to 10,000 amu/q [Coates, A.J., Crary, F.J., Lewis, G.R., Young, D.T., Waite Jr., J.H., Sittler Jr., E.C., 2007. Discovery of heavy negative ions in Titan's ionosphere. Geophys. Res. Lett.…
Saturn's north polar cyclone and hexagon at depth revealed by Cassini/VIMS
Nicholson, Philip D.; Fletcher, Leigh N.; Baines, Kevin H. +6 more
A high-speed cyclonic vortex centered on the north pole of Saturn has been revealed by the visual-infrared mapping spectrometer (VIMS) onboard the Cassini-Huygens Orbiter, thus showing that the tropospheres of both poles of Saturn are occupied by cyclonic vortices with winds exceeding 135 m/s. High-spatial-resolution (~200 km per pixel) images acq…
Plasma in Saturn's nightside magnetosphere and the implications for global circulation
Coates, A. J.; Dougherty, M. K.; Thomsen, M. F. +8 more
We present a bulk ion flow map from the nightside, equatorial region of Saturn's magnetosphere derived from the Cassini CAPS ion mass spectrometer data. The map clearly demonstrates the dominance of corotation flow over radial flow and suggests that the flux tubes sampled are still closed and attached to the planet up to distances of 50 RS
Isotopic evolution of the major constituents of Titan's atmosphere based on Cassini data
Mousis, Olivier; Mandt, Kathleen E.; Waite, J. Hunter +5 more
Using Cassini ion neutral mass spectrometer stable isotope observations, we have developed a comprehensive method for modeling the time-evolution of the stable isotopic ratios in Titan's major constituents, N 2, CH 4 and H 2. Our model provides constraints on the initial 14N/ 15N ratio in N