HR: 14:20h
AN: SA33C-02    [Abstracts]
TI: Solar Forcing and the Variability of the Planetary Ion Escape from Mars
AU: * Lundin, R
EM: rickard.lundin@irf.se
AF: Swedish Institute of Space Physics (IRF), Box 812, Kiruna, 981 28, Sweden
AU: Perez-de-Tejada, H
EM: perezdet@geofisica.unam.mx
AF: Institute of Geophysics, UNAM, Mexico, Mexico
AU: Barabash, S
EM: stas@irf.se
AF: Swedish Institute of Space Physics (IRF), Box 812, Kiruna, 981 28, Sweden
AU: Nilsson, H
EM: hans.nilsson@irf.se
AF: Swedish Institute of Space Physics (IRF), Box 812, Kiruna, 981 28, Sweden
AU: Yamauchi, M
EM: yamau@irf.se
AF: Swedish Institute of Space Physics (IRF), Box 812, Kiruna, 981 28, Sweden
AB: An orbit-by-orbit study with ASPERA-3 on Mars Express indicates a great variability of the ionospheric ion outflow from Mars. The study comprises 46 orbits covering a range of solar wind parameters. Solar wind conditions were determined during inbound and outbound, assuming stable solar wind conditions throughout the traversal of the Mars induced magnetosphere. A comparision between planetary ion outflow and the solar wind/sheath flux was made. The study shows evidence for a strong coupling between ion escape and solar wind momentum and energy flux. A fairly high correlation coefficient (R=0.85) between the solar wind dynamic pressure and the ion escape mass flux is obtained. The inferred ion escape mass flux varied up to two orders of magnitude. The good correlation agrees with the hypothesis of a direct energy- and momentum transfer between the solar wind and the ionospheric plasma at Mars. By normalizing the Mars obstacle response/size with the solar wind/sheath flux we obtain and increased correlation coefficient (R=0.95). The improved correlation can be interpreted as an EUV/UV control of the obstacle size, since the obstacle size (ionospheric boundary) without any changes of EUV/UV should be entirely controlled by solar wind parameters. We argue that the strong variability of the escape flux from Mars is the consequence of the variability in solar forcing, the solar forcing originating from the solar wind energy- and momentum flux, and solar EUV/UV. We note that the solar EUV/UV and solar wind forcing are not necessarily coincident, considering the difference in travel time to the planet.
DE: 6225 Mars
DE: 6295 Venus
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly