HR: 1340h
AN: P43A-1031    [Abstracts]
TI: Determination of Ionization Rates in the E ring Based on Magnetic Fluctuation Amplitudes
AU: Cowee, M M
EM: mcowee@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, UCLA, 405 Hilgard Ave, Los Angeles, CA 90095, United States
AU: * Omidi, N
EM: omidi@solanasci.com
AF: Solana Scientific Inc, 777 S. Pacific Coast HWY Suite 208-B, Solana Beach, CA 92075, United States
AU: Leisner, J S
EM: jleisner@ess.ucla.edu
AF: Institute of Geophysics and Planetary Physics, UCLA, 405 Hilgard Ave, Los Angeles, CA 90095, United States
AU: Russell, C T
EM: ctrussel@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, UCLA, 405 Hilgard Ave, Los Angeles, CA 90095, United States
AU: Torkar, R L
EM: rlt@lanl.gov
AF: ISR-1, Space and Atmospheric Sciences, Los Alamos National Laboratory, P.O. Box 1663, MS D466, Los Alamos, NM 87545, United States
AU: Blanco-Cano, X
EM: xbc@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Ciudad Universitaria, Coyoacan, D.F. 04510, Mexico
AB: Recent Cassini observations have established that the icy moon Enceladus is actively venting and ejecting water molecules, indicating strongly that it is the origin of the torus atmosphere. The interaction between the corotating plasma and neutrals is a critical process with significant implications for the evolution of both. Ionization of the neutral gasses through charge exchange creates a population of slower moving ions which interact with the corotating plasma and gain energy. When neutralized, these ions form faster moving neutrals that travel to larger radial distances from Saturn or escape from the system. Ionization of neutrals leads to a velocity phase space distribution function known as a ring distribution which results in generation of ULF waves in the torus and can be used for determining the ionization rates throughout the region. To do so, it is necessary to establish the saturation amplitude of the waves as a function of ionization rate. Given the nonlinear nature of this process, we use 2.5-Dimensional electromagnetic hybrid (kinetic ions, fluid electrons) simulations to investigate the generation and nonlinear evolution of ion cyclotron and mirror waves by ring distribution functions. Specifically, we utilize Cassini plasma measurements at a number of different radial distances in the E ring to initialize the simulations and determine the ionization rates needed to account for the observed wave amplitudes at these distances. Assuming charge exchange to be the dominant ionization process, we also estimate neutral densities at these distances and compare to model predictions.
DE: 2152 Pickup ions
DE: 2732 Magnetosphere interactions with satellites and rings
DE: 2753 Numerical modeling
DE: 2772 Plasma waves and instabilities (2471)
DE: 6280 Saturnian satellites
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting