HR: 08:55h
AN: P51D-04    [Abstracts]
TI: The electron density structure of the Titan ionosphere
AU: * Kliore, A J
EM: akliore@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr, Pasadena, CA 91109, United States
AU: Nagy, A F
EM: anagy@umich.edu
AF: Univeresity of Michigan, 2455 Hayward Ave, Ann Arbor, MI 48109, United States
AU: Flasar, F M
AF: NASA/Goddard Space Flight Center, Code 693, Greenbelt, MD 20771, United States
AU: Schinder, P F
AF: Cornell University annd NASA Goddard Space Flight Center, Code 693, Greebelt, MD 20071, United States
AU: French, R G
AF: Wellesley College, Astronomy Department, Wellesley, MA 02181, United States
AU: Marouf, E A
AF: San Jose State University, One Washington Square, San Jose, CA 95192, United States
AU: Rappaport, N J
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr, Pasadena, CA 91109, United States
AU: Anabtawi, A
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr, Pasadena, CA 91109, United States
AU: McGhee, C A
AF: Wellesley College, Astronomy Department, Wellesley, MA 02181, United States
AB: Eight vertical profiles of the electron density in Titan's ionosphere were derived from the Cassini radio occultations of March 26, and May28, 2007 (T27 and T31), as well as those of March 19, 2006 (T12), and May 20,2006 (T14) . The 2006 occultations occurred at low Southern latitudes of 14.7S, 36.2S, 19.8S, and 21.9S. The 2007 occultations were nearly polar, at latitudes of 75S and 61N for T27. and 75S and 74N for T31.. The solar zenith angles for all occultations were near the terminator, ranging from 85 to 95 deg. The ionosphere peak was observed to lie close to an altitude of 1200 km, and the observed peak densities ranged from about 1.2 to 2.2 x 103 cm-3, which is in good agreement with other Cassini observations and the previous Voyager radio occultation results. In all measurements, the peak densities are about 30% higher near the dusk terminator, showing the influence of solar EUV. Radio occultation observations of the Titan ionosphere are difficult because of its low density and small size, and it was facilitated by the unprecedented Cassini radio science system, which has three frequencies that can operate simultaneously: S-band (2.3 GHz), X-band (8.4 GHz), and Ka-band (32 GHz). In particular, Ka-band had never been used before to probe Titan's ionosphere, and the signal-to-noise ratios at all frequencies of 42, 54, and 48 dB-Hz., respectively, have never before been achieved. The results indicate a clear dusk-dawn asymmetry in peak electron density, with the average dusk density being about 450% greater than the dawn side. . The dusk profiles also have more structure both above and below the main peak, including a peak at about 500 km. altitude.
DE: 2459 Planetary ionospheres (5435, 5729, 6026)
DE: 6281 Titan
DE: 6929 Ionospheric physics (1240, 2400)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting