HR: 1340h
AN: P33B-1302    [Abstracts]
TI: Solar Wind Plasma Pile-up at the Magnetic Polar Regions of the Venus Ionosphere: Viscous Force Effects
AU: * Perez-de-Tejada, H
EM: perezdet@geofisica.unam.mx
AF: Institute of Geophysics, UNAM, Ciudad Universitaria, Mexico City, DF 04510, Mexico
AU: Lundin, R
EM: rickard.lundin@irf.se
AF: Swedish Institute of Space Physics, Teknikhuset, Umea, SE-901 87, Sweden
AU: Reyes-Ruiz, M
EM: maurey@astrosen.unam.mx
AF: Institute of Astronomy, UNAM, Baja California, Ensenada, BC 2860, Mexico
AB: Measurements conducted with the Mariner 5 and the Venus Express spacecraft near the Venus ionosphere reveal the presence of accumulated plasma fluxes located upstream from the polar regions. Along the Mariner 5 trajectory the plasma and magnetic field data show evidence of enhanced values of the plasma density, temperature, and magnetic field intensity, with a sharp change in the solar wind speed by the terminator at a position located nearly 4000 km above the planetary surface. This event was detected when the spacecraft was situated much farther away than the expected position of the ionopause at the terminator and suggests conditions unrelated to the pile-up of the solar wind over the latter boundary around the subsolar region. Similar conditions are inferred from measurements conducted with the ASPERA instrument in the Venus Express spacecraft which show data with enhanced plasma fluxes detected through regions that extend far upstream from the terminator. The presence of such enhanced plasma fluxes is interpreted as resulting from a drastic slow down that the solar wind experiences at the magnetic polar regions through momentum transferred to the upper ionosphere. The results of a numerical simulation of the solar wind interaction with the Venus ionosphere including viscous forces support the accumulation of the incident plasma fluxes upstream from the magnetic polar regions and lead to values of the Reynolds number and the Mach number that are consistent with those inferred from the geometry of the viscous boundary layer that extends downstream from them.
DE: 2459 Planetary ionospheres (5435, 5729, 6026)
DE: 5421 Interactions with particles and fields
DE: 5440 Magnetic fields and magnetism
DE: 5462 Polar regions
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting