HR: 15:45h
AN: P33B-07    [Abstracts]
TI: Mars and Venus ion cyclotron waves and their implications
AU: Wei, H
EM: hwei@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, United States
AU: * Russell, C
EM: ctrussel@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, United States
AU: Leisner, J
EM: jleisner@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, United States
AU: Zhang, T
EM: Tielong.Zhang@oeaw.ac.at
AF: Space Research Institute, Austrian Academy of Sciences, OEAW, Graz, 8042, Austria
AU: Blanco-Cano, X
EM: xbc@geofisica.unam.mx
AF: Institute of Geophysics, UNAM, Ciudad Universitaria, Coyocan, 04510, Mexico
AB: Mars and Venus do not have appreciable global magnetic fields to shield their neutral atmospheres from erosion by the solar wind. When their atmospheric hydrogen atoms are ionized and picked up by the solar wind, proton cyclotron waves are created from the free energy of the ring-beam distribution of the pick-up ions. At Mars, proton cyclotron waves observed by Mars Global Surveyor extend from the magnetosheath to over 12 Mars radii, with intermittent occurrence and amplitudes slowly varying with distance. The wave occurrence pattern indicates that the Martian hydrogen exosphere cannot be spherically symmetric but is rather disk- shaped with asymmetry in the direction of the interplanetary electric field. In order to travel across the magnetic field the picked up ions must be neutralized near where they are picked up and these fast neutrals are transported to distant regions where they get re-ionized and produce waves far downstream. Thus the top of Mars exosphere appears to extend in a disk to high altitude, with its orientation controlled by the interplanetary magnetic field. At Venus, proton cyclotron waves were first observed in the magnetosheath by Pioneer Venus Orbiter and later in the solar wind around Venus by Venus Express at a distance as far as 7 Venus radii. This paper compares the properties of the Mars and Venus waves and discusses the implication of these observations.
DE: 2152 Pickup ions
DE: 2471 Plasma waves and instabilities (2772)
DE: 2780 Solar wind interactions with unmagnetized bodies
DE: 6225 Mars
DE: 6295 Venus
SC: Planetary Sciences [P]
MN: 2009 Joint Assembly