INVESTIGADORES
BERTUCCI Cesar
congresos y reuniones científicas
Título:
The Structure of the Martian and Venusian Magnetic Pileup Boundaries
Autor/es:
BERTUCCI, C.; MAZELLE, C.; ACUNA, M. H.; SLAVIN, J. A.; RUSSELL, C. T.
Reunión:
Congreso; AGU Fall Meeting 2003; 2003
Resumen:
The lack of global-scale intrinsic magnetic fields and the presence of
an atmosphere at Mars, Venus and comets makes their interactions with
the solar wind very similar, with the formation of a magnetic barrier in
front of a highly conducting obstacle and an induced magnetic tail as
their most prominent features. A sharp plasma boundary marks the entry
into the magnetic barrier: the Magnetic Pileup Boundary (MPB). At Mars,
the MPB has been identified by very clear observational signatures,
including a gradient in the magnetic field magnitude (often as a sharp
jump) 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 more numerous. Recently, the presence of
another MPB signature, the enhancement of the magnetic field draping,
allowed to identify this boundary also at Venus. We study the magnetic
structure of the magnetic pileup boundary at Mars and Venus by
performing minimum variance analysis on Mars Global Surveyor and Pioneer
Venus Orbiter magnetic field measurements. For each one of the crossings
analyzed, we obtain a very well defined normal vector to the current
sheet. At Mars, its direction is in very good agreement with the normal
vector deduced from a fit of the Martian MPB. We also study its
thickness compared to physical scales, as well as its temporal
variations. The results confirm that the MPB is a well-defined plasma
boundary, whose magnetic structure usually resembles to a tangential
discontinuity in the strict MHD sense. However, its nature seems to be
rather explicable from multi-fluid or hybrid approaches. Finally, we
compare our results with similar observations at the MPB of comets and
at the tail boundary of Venus.