University of Kansas Titan Studies

Draft The Ionosphere of Titan: An Updated Theoretical Model T. E. Cravens et al.

Image courtesy of NASA/JPL-Caltech.

Introduction

A wide variety of ionospheres exist in the solar system, and similar basic physical and chemical processes can lead to very different ionospheres (cf. Nagy and Cravens, 2002). Titan appears to have a particularly interesting ionosphere which is produced both by photoionization by solar radiation and by impact ionization by magnetospheric electrons (cf. Cravens et al., 1992; Nagy and Cravens, 2002; Banaskiewicz et al., 2000). Many models of the upper atmosphere and ionosphere of Titan have been developed since the Voyager 1 encounter with this satellite in November 1980 (e.g., Ip, 1990; Keller et al., 1992; Gan et al., 1992; Roboz and Nagy, 1994; Fox and Yelle, 1997; Keller et al., 1998; Galand et al., 1999; Banaskiewicz et al., 2000), but these models are largely based on the data returned from this one encounter. Just a single electron density profile was measured using the radio occultation experiment (Bird et al., 1997). Models of the neutral upper atmosphere have been constrained by data from the Voyager ultraviolet spectrometer (Smith et al., 1982; Strobel, 1982) and from infrared observations (e.g., Coustenis et al., 1989). Motivations for the extensive model development for Titan's atmosphere and ionosphere include the interesting and unique hydrocarbon chemistry which takes place at the satellite and the data which is expected from the Cassini mission to the Saturn system.

Results from an updated theoretical model of the ionosphere of Titan are presented in the current paper. The focus is on the effects of ionizing solar photons on the ionosphere of Titan rather than on the effects of magnetospheric electrons. Production within the ionosphere of Auger electrons resulting from "K-shell" ionization is included in the model.

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Last modified April 14, 2004 Tizby Hunt-Ward tizby@ku.edu