HR: 1340h
AN: SA13A-1114    [Abstracts]
TI: LOW-ALTITUDE IONOSPHERIC PLASMA ENERGIZATION AT MARS - ASPERA-3 FINDINGS
AU: * Lundin, R N
EM: rickard.lundin@irf.se
AF: Swedish Institute of Space Physics, Box 812, Kiruna, SE-981 28 Sweden
AB: The Analyzer of Space Plasma and Energetic Atoms (ASPERA) on-board the Mars Express spacecraft (MEX) found that the solar wind plasma and accelerated ionospheric ions may be observed all the way down to the MEX pericenter of 270 km above the dayside planetary surface. This is very deep in the ionosphere, implying a direct exposure of the martian topside atmosphere to solar wind plasma forcing. The solar wind forcing results in an energization of ionospheric plasma. The low-altitude ion energization and outflow near Mars is surprisingly similar to the ion energization and outflow over the strongly magnetized planet Earth - from narrow "monoenergetic" ion beams to beams with a broad energy distribution. The ion outflow near the planet is in the direction of the external sheath flow, i.e. the ion energization is the result of a localized and direct solar wind momentum exchange. On the other hand the distribution of the energized plasma implies similar energization processes like that over the Earth, i.e. energization in a magnetized environment by waves and/or parallel (to B) electric fields. But the boundary conditions for Martian plasma energization is different from that of the Earth - a weak local magnetic field and penetration of solar wind plasma deep into a cold and dense ionospheric plasma. This report will be discuss results from the first year of ASPERA-3 investigations on the low-altitude energization of plasma near Mars.
DE: 6006 Atmospheres--evolution
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting