HR: 0800h
AN: P51A-1410    [Abstracts]
TI: Nonlinear electrostatic structures associated with Saturn's bow shock
AU: * Chen, L
EM: li-jen-chen@uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Van Allen Hall, Iowa City, IA 52242 United States
AU: Gurnett, D
AF: University of Iowa, Department of Physics and Astronomy, Van Allen Hall, Iowa City, IA 52242 United States
AU: Kurth, W
AF: University of Iowa, Department of Physics and Astronomy, Van Allen Hall, Iowa City, IA 52242 United States
AU: Rymer, A
AF: University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, RH5 6NT United Kingdom
AU: Dougherty, M
AF: Imperial College, Department of Physics, Imperial College London, South Kensington campus, London, SW7 2AZ United Kingdom
AU: Crary, F
AF: Southwest Research Institute, Space Science and Engineering Division, San Antonio, TX 78238 United States
AU: Karoly, S
AF: University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, RH5 6NT United Kingdom
AB: We report on nonlinear electrostatic structures including pulse chains and isolated pulses observed to be abundant at the bow shock transition layer and the downstream magnetosheath of Saturn. The characteristic time scales involved in these nonlinear structures are 5-10 ms. Pulse chains, isolated pulses, and large amplitude (up to $\sim$ 10 mV/m) fluctuations of very similar time scales are also observed to be the dominant waveforms in the downstream bow shock current layer at Earth. Considering the widely different densities and magnetic field strengths in the two magnetosheaths, we rule out those wave modes whose characteristic frequencies scale with the plasma frequency or the cyclotron frequency. The only parameters that are comparable in the two magnetosheaths are the plasma streaming velocity and the electron temperature. We therefore conclude that the responsible wave mode is the low frequency (below the ion plasma frequency) ion acoustic mode. The solitary unipolar, bipolar, and tripolar electric-field structures of these time scales are thus most likely to be nonlinear descendants of low frequency ion acoustic waves. These nonlinear electrostatic structures may hold important information on how a collisionless shock boundary is formed and sustained.
DE: 6275 Saturn
DE: 2154 Planetary bow shocks
DE: 2712 Electric fields (2411)
DE: 2728 Magnetosheath
DE: 2784 Solar wind/magnetosphere interactions
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting