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Título:
Structure and variability of the Martian MPB and Bow Shock from MGS MAG/ER observations
Autor/es:
BERTUCCI, C.; MAZELLE, C.; ACUNA, M.
Reunión:
Congreso; 35th COSPAR Scientific Assembly; 2004
Resumen:
The observations of the MAG/ER (Magnetometer / Electron Reflectometer)
investigation aboard Mars Global Surveyor (MGS) during the aerobraking
phase around Mars allowed a deep characterization of the bow shock and
the magnetic pileup boundary (MPB). The Martian bow shock crossings are
identified by an increase in the magnetic field magnitude and in its
fluctuation level, and a simultaneous increase in the superthermal
fluxes, as the plasma is compressed and heated. All these crossings
display a complex structure, even when the angle between the shock
normal and the magnetic field is close to 90 degrees. This feature makes
Mars' bow shock more similar to comets' than Venus'. On the other hand,
the MPB is perhaps one of the most spectacular features in the
Mars-Solar wind interaction. This boundary represents the outer edge of
the magnetic barrier. At Mars and comets, the MPB has been identified by
very clear observational signatures, including a strong gradient in the
magnetic field magnitude accompanied by a decrease in the magnetic field
fluctuations and a drastic decrease in the solar wind electron and
proton densities, as exospheric-induced ions become dominant. A recenty
discovered MPB feature, the enhancement of the magnetic field line
draping, allowed to identify this boundary also at Venus. In this talk
we analyze the structure, location and variability of these two
boundaries from MGS MAG/ER data and we discuss the influence of
different factors as solar cycle, upstream solar wind conditions, and
mass loading. The role of the exosphere / ionosphere in their nature and
behavior is also studied.