HR: 09:45h
AN: P31D-08    [Abstracts]
TI: Calculation of Loss Rate from Saturn's E Ring
AU: * Leisner, J S
EM: jleisner@ess.ucla.edu
AF: IGPP/UCLA, Box 951567, Los Angeles, CA 90095
AU: Russell, C T
EM: ctrussell@igpp.ucla.edu
AF: IGPP/UCLA, Box 951567, Los Angeles, CA 90095
AU: Dougherty, M K
EM: m.dougherty@imperial.ac.uk
AF: Imperial College, London, Blackett Lab Space & Atmos Physics, London, SW7 2AZ United Kingdom
AU: Blanco-Cano, X
EM: xbc@geofisica.unam.mx
AF: UNAM, Ciudad Universitaria Instituto Geofisica, Coyoacan, DF 4510 Mexico
AU: Strangeway, R J
EM: strange@igpp.ucla.edu
AF: IGPP/UCLA, Box 951567, Los Angeles, CA 90095
AU: Strangeway, R J
EM: strange@igpp.ucla.edu
AF: Imperial College, London, Blackett Lab Space & Atmos Physics, London, SW7 2AZ United Kingdom
AU: Bertucci, C
EM: c.bertucci@imperial.ac.uk
AF: Imperial College, London, Blackett Lab Space & Atmos Physics, London, SW7 2AZ United Kingdom
AU: Bertucci, C
EM: c.bertucci@imperial.ac.uk
AF: UNAM, Ciudad Universitaria Instituto Geofisica, Coyoacan, DF 4510 Mexico
AB: Ionization--whether through solar photons, impacting particles, or charge exchange--is a significant loss process in the neutral E ring. When these particles are ionized, they are energized by the electric field associated with the corotating magnetized plasma. If the pick-up energy is great enough, the particles generate ion cyclotron waves with a magnetic field amplitude that is determined by the energy of the pick-up ions. These waves, with frequencies near the local water-group gyrofrequencies, were first seen in the E ring by the Pioneer 11 and Voyager 1 magnetometers, but it is Cassini's large coverage of radial distance, local time, and latitude within the E ring that allows us to use this spacecraft's magnetometer to conduct a comprehensive study of these waves. Using a simple plasma profile and modeling the E ring as a mass source in the equatorial plane, we use the ion cyclotron waves to calculate the ionization rate through the ring. We find that between 3.5 and 7 Rs, the E ring loses a total of 6 x 10²⁶ neutrals, or 18 kilograms of H₂O, per second. This total is about one fourth of the amount expected from previous models and the radial erosion rate agrees qualitatively with E ring density profiles, except at 4.6 Rs. Using the ion cyclotron waves, our calculations show a discontinuity in the erosion rate at that equatorial distance and all latitudes. This discontinuity can not be explained with the assumed smoothly varying plasma profiles or production rates.
DE: 5737 Magnetospheres (2756)
DE: 5759 Rings and dust
DE: 6265 Planetary rings
DE: 6275 Saturn
SC: Planetary Sciences [P]
MN: Fall Meeting 2005