HR: 1340h
AN: P23A-0237    [Abstracts]
TI: Friction Layer at the Sides of the Plasma Channels in the Venus Nightside Ionosphere
AU: * Perez-de-Tejada, H A
EM: perezdet@igeofcu.unam.mx
AF: Hector Perez-de-Tejada, Institute of Geophysics, National University of Mexico, Mexico City, DF 04510 Mexico
AB: Electron density signatures of the Venus ionosphere measured with the Pioneer Venus Orbiter (PVO) show passes in which the density profile exhibits a plateau shape that extends across a significant section of the upper ionosphere. Such cases are not seen throughout the nightside hemisphere but occur mostly near the midnight plane. A distribution of the number of cases with this peculiarity was obtained from 20 PVO passes of a set of 40 PV orbits that scanned the nightside ionosphere in the first and third season of operation. The distribution shows that the location where the density plateau is observed is slightly shifted from the midnight plane towards the dawn side thus suggesting a displacement in the same direction as that of the distribution of ionospheric holes reported from the early PVO measurements. The peak of the distribution occurs near 1 hr LST and thus its displacement from the midnight plane is slightly smaller than that of the ionospheric holes. With this information it is argued that a friction layer is formed along the sides of the plasma channels with a tendency for the profiles with the density plateau to preferably occur in the dusk side of those features. This result is viewed as implying that the ionospheric material located in that side of the plasma channels, which serve to interpret the ionospheric holes, is more strongly eroded by the solar wind that flows within the channels. It is further suggested that the dusk-dawn difference in the location of the plateau-shaped density profiles across the ionospheric holes may result from the effects of a rotational motion of the upper ionosphere on the solar wind that flows within the plasma channels. The kinetic pressure that is exerted by the rotating ionosphere on the solar wind at the dusk side of the channels implies the large ionospheric erosion seen in that side and hence the profiles with the density plateau.
DE: 4899 General or miscellaneous
DE: 5407 Atmospheres--evolution
DE: 5421 Interactions with particles and fields
DE: 5462 Polar regions
DE: 2459 Planetary ionospheres (5435, 5729, 6026, 6027, 6028)
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting