Journal
PLANETARY AND SPACE SCIENCE
Volume 56, Issue 1, Pages 3-18Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.pss.2007.06.006
Keywords
saturn; magnetosphere; plasmasphere; plasma; magnetic fields; ion-neutral sources
Categories
Funding
- Science and Technology Facilities Council [PP/E001173/1] Funding Source: researchfish
- STFC [PP/E001173/1] Funding Source: UKRI
Ask authors/readers for more resources
Using ion-electron fluid parameters derived from Cassini Plasma Spectrometer (CAPS) observations within Saturn's inner magnetosphere as presented in Sittler et al. [2006a. Cassini observations of Saturn's inner plasmasphere: Saturn orbit insertion results. Planet. Space Sci., 54, 1197-1210], one can estimate the ion total flux tube content, NIONL2, for protons, H+, and water group ions, W+, as a function of radial distance or dipole L shell. In Sittler et al. [2005. Preliminary results on Saturn's inner plasmasphere as observed by Cassini: comparison with Voyager. Geophys. Res. Lett. 32(14), L14S04), it was shown that protons and water group ions dominated the plasmasphere composition. Using the ion-electron fluid parameters as boundary condition for each L shell traversed by the Cassini spacecraft, we self-consistently solve for the ambipolar electric field and the ion distribution along each of those field lines. Temperature anisotropies from Voyager plasma observations are used with (T-perpendicular to/T-II)(w+)similar to 5 and (T-perpendicular to/T-II)(H+)similar to 2. The radio and plasma wave science (RPWS) electron density observations from previous publications are used to indirectly confirm usage of the above temperature anisotropies for water group ions and protons. In the case of electrons we assume they are isotropic due to their short scattering time scales. When the above is done, our calculation show NIONL2 for H+ and W+ peaking near Dione's L shell with values similar to that found from Voyager plasma observations. We are able to show that water molecules are the dominant source of ions within Saturn's inner magnetosphere. We estimate the ion production rate S-ION similar to 10(27) ions/s as function of dipole L using NH+, Nw+ and the time scale for ion loss due to radial transport tau(D) and ion-electron recombination tau(REC). The ion production shows localized peaks near the L shells of Tethys, Dione and Rhea, but not Enceladus. We then estimate the neutral production rate, S-w, from our ion production rate, S-ION, and the time scale for loss of neutrals by ionization, tau(ION), and charge exchange, tau(CH). The estimated source rate for water molecules shows a pronounced peak near Enceladus' L shell L similar to 4, with a value S-w similar to 2 x 10(28) mol/s. (c) 2007 Elsevier Ltd. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available