HR: 14:00h
AN: P43A-01 INVITED     [Abstracts]
TI: Interactions Between Neutral Gas Clouds and Plasma Near the icy satellites of Jupiter and Saturn.
AU: * Burger, M H
EM: matthew.burger@gsfc.nasa.gov
AF: NASA Postdoctoral Program, NASA/GSFC, Code 673 8800 Greenbelt Rd, Greenbelt, MD 20771, United States
AB: Neutral gas clouds associated with icy satellites are intimately tied to the magnetospheric plasma in which they are formed and reside. Plasma interactions can create the clouds, remove material from them, and make it possible for us to observe them. At Europa, for example, energetic ions incident on the icy surface eject hydrogen and oxygen formed from the dissociation of water (Johnson et al. 1982). The hydrogen escapes, but the O₂remains gravitationally bound, forming an atmosphere. This atmosphere then interacts with the thermal plasma in Jupiter's magneotpshere: the O₂is dissociated by the electrons resulting in emissions from atomic oxygen which have been observed by HST and Cassini (Hall et al. 1995; Hansen et al. 2005). Charge exchange with magnetospheric ions and electron-impact ionization removes atoms and molecules from Europa's atmosphere and exosphere, and contributes fresh ions to the plasma (Saur et al. 1998; Shematovich et al 2005). At Enceladus, where 150-300 kg/s of H₂O gas is supplied by the south pole plume (Hansen et al. 2006; Burger et al. 2007), charge exchange reactions between the plasma and H₂O produce fresh pickup ions which slow and deflect the plasma (Tokar et al. 2006; Pontius and Hill 2006) and induce perturbations in Saturn's magnetic field (Dougherty et al. 2006; Khurana et al. 2006). The neutrals created in these charge exchange reactions either escape from Saturn entirely or are redistributed throughout the inner magnetosphere forming gas clouds which have been observed by HST and Cassini (Johnson et al. 2006). I will describe the interaction processes between the neutral atoms and molecules in icy satellite atmospheres and exospheres, and discuss differences between the processes imporant in Jupiter's magnetosphere, where the plasma content is greater than the neutral content, and Saturn's magnetosphere, which is dominated by neutrals. References: Burger et al., JGR, 2007, in press. Dougherty et al., Science, 311, 1406, 2006. Hall et al., Nature, 373, 677, 1995. Hansen et al. Icarus, 176, 305, 2005. Hansen, et al., Science, 311, 1422, 2006. Johnson et al., Nucl. Inst. Meth., 198, 829, 1982. Johnson, et al., ApJ, 644, L137, 2006. Khurana et al., JGR, 2007, submitted. Pontius and Hill, JGR, 111, A09214, 2006. Saur et al., JGR, 103, 19947, 1998. Shematovich et al., Icarus, 173, 480, 2005. Tokar et al. 2006, JGR, 311, 1409, 2006.
DE: 5421 Interactions with particles and fields
DE: 6033 Magnetospheres (2756)
DE: 6045 Physics and chemistry of materials
DE: 6218 Jovian satellites
DE: 6280 Saturnian satellites
SC: Planetary Sciences [P]
MN: 2007 Joint Assembly