HR: 1340h
AN: P43A-0946    [Abstracts]
TI: Whistlers Observed in the Magnetosphere of Saturn
AU: * Akalin, F
EM: ferzan-akalin@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Gurnett, D A
EM: donald-gurnett@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Averkamp, T F
EM: terrance-averkamp@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Persoon, A M
EM: ann-persoon@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Santolik, O
EM: ondrej.santolik@mff.cuni.cz
AF: University of Iowa, Dept. of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Santolik, O
EM: ondrej.santolik@mff.cuni.cz
AF: Charles University, Faculty of Mathematics and Physics, Prague, CZ-18000 Czech Republic
AU: Kurth, W S
EM: william-kurth@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Hospodarsky, G B
EM: george-hospodarsky@uiowa.edu
AF: University of Iowa, Dept. of Physics and Astronomy, Iowa City, IA 52242 United States
AB: Whistlers generated by lightning have been observed in the magnetosphere of Saturn by the Cassini Radio and Plasma Wave Science (RPWS) instrument. Three events have been observed, two on July 1, 2004, and one on October 28, 2004. We have concentrated our analysis on the event that occurred on October 28 because it is more clearly defined than the other two. This whistler was observed during the inbound pass of orbit A at a radial distance of 6.19 R_S (Saturn radii) and a latitude of 12.3 degrees. The whistler has a good fit to the Eckersley law with a dispersion constant of 81 Hz^1/2 sec. Because the computed dispersion is too small to be consistent with a southern hemisphere source, it is believed that the whistler originated from lightning in the northern hemisphere of Saturn. To compute the dispersion, we use a centrifugal Gaussian scale height model for the ions and assume that the plasma consists of hydrogen ions and the water group ions. We find that the observed dispersion can be explained if the equatorial fractional concentration of water group ions is 0.84, with a scale height of 1.08 R_S, and the equatorial fractional concentration of hydrogen ions is 0.16, with a scale height of 4.32 R_S. These results have been compared to a more complex diffusive equilibrium model. For each species, the parallel pressure balance equation has been solved by integrating along the field line, including the pressure gradient force, the centrifugal force, and the gravitational force. Even though there are slight differences, both models give very similar results.
DE: 2467 Plasma temperature and density
DE: 2756 Planetary magnetospheres (5443, 5737, 6033)
DE: 6245 Meteors
SC: Planetary Sciences [P]
MN: Fall Meeting 2005