HR: 16:40h
AN: SH22C-03    [PDF]
TI: The Interstellar Hydrogen Shadow: Observations of Interstellar Pickup Ions Beyond Jupiter
AU: * McComas, D J
EM: dmccomas@swri.edu
AF: Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228 United States
AU: Schwadron, N A
EM: nschwadron@swri.edu
AF: Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228 United States
AU: Crary, F J
EM: fcrary@swri.edu
AF: Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228 United States
AU: Elliott, H A
EM: helliott@swri.edu
AF: Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228 United States
AU: Young, D T
EM: dyoung@swri.edu
AF: Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228 United States
AU: Gosling, J T
EM: jgosling@lanl.gov
AF: Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
AU: Thomsen, M
EM: mthomsen@lanl.gov
AF: Los Alamos National Laboratory, MS D466, Los Alamos, NM 87545 United States
AU: Sittler, E C
EM: edward.c.sittler@nasa.gov
AF: NASA Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
AU: Berthelier, J
EM: jean-jacques.berthelier@cetp.ipsl.fr
AF: CNRS, 4 Avenue de Neptune, St. Maur, 94100 France
AU: Szego, K
EM: szego@rmki.kfki.hu
AF: KFKI Research Institute for Particles and Nuclear Physics, POB 49, Budapest, H-1525 Hungary
AU: Coates, A J
EM: ajc@mssl.ucl.ac.uk
AF: University College London, MSSL, Holmbury St Mary/Dorking, Surrey, RH5 6NT United Kingdom
AB: This study analyzes the first observations of heliospheric pickup ions beyond the orbit of Jupiter. The Cassini Plasma Spectrometer observes H+, He+, He++, and O+ pickup ions of interstellar origin between 6.4 and 8.2 AU. Surprisingly, however, there is a strong depletion of pickup H+ compared to He+, in contrast to the interstellar H/He ratio of approximately 10. We show that this depletion is produced by a combination of gravitational focusing of He by the Sun and a newly observed "interstellar hydrogen shadow" that diminishes the source of pickup H as Cassini moves through the region behind the Sun relative to the local interstellar flow. Most H atoms cannot penetrate into this downstream shadow region since to get there they must pass close by the Sun where they have a high probability of being ionized and swept out with the solar wind.
DE: 2114 Energetic particles, heliospheric (7514)
DE: 2124 Heliopause and solar wind termination
DE: 2134 Interplanetary magnetic fields
DE: 2144 Interstellar gas
DE: 2152 Pickup ions
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting