HR: 16:35h
AN: SM34A-02    [Abstracts]
TI: Upstream Cyclotron Waves from Venus Express Observations
AU: * Delva, M
EM: magda.delva@oeaw.ac.at
AF: Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6 , GRAZ, A 8042, Austria
AU: Zhang, T
EM: tielong.zhang@oeaw.ac.at
AF: Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6 , GRAZ, A 8042, Austria
AU: Volwerk, M
EM: martin.volwerk@oeaw.ac.at
AF: Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6 , GRAZ, A 8042, Austria
AU: Volwerk, M
EM: martin.volwerk@oeaw.ac.at
AF: Max Plank Institute for Extraterrestrial Physics Germany, P.O.B. 1312, Garching, D-85741, Germany
AU: Russell, C T
EM: ctrussel@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California Los Angeles , Slichter Hall, Los Angeles, CA 90095-1567, United States
AU: Wei, H
EM: hwei@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California Los Angeles , Slichter Hall, Los Angeles, CA 90095-1567, United States
AB: The escape of particles from planetary atmospheres, especially hydrogen, is an important key towards understanding the atmospheric composition and evolution over the lifetime of the solar system. For an unmagnetized planet such as Venus or Mars when the neutral exosphere extends into the flowing solar wind plasma, loss of pick-up ions can play a significant role. Cyclotron waves from pick-up hydrogen in the solar wind have been previously observed at Mars but not at Venus. Here we report proton-cyclotron waves seen well upstream from the planet both outside and inside the planetary foreshock region, giving direct evidence that the solar wind is removing hydrogen from the planetary exosphere. Properties of the wave-occurrences are extensively studied and statistics are shown, i.e. specific aspects of the spectra, analysis in the magnetic field principal axes system, direction of propagation. The proton cyclotron waves appear to be intermittent; moreover, from PVO observations there were not reported. This raises the question why the situation at Venus is so different from Mars.
DE: 2134 Interplanetary magnetic fields
DE: 2159 Plasma waves and turbulence
DE: 2780 Solar wind interactions with unmagnetized bodies
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly