INVESTIGADORES
BERTUCCI Cesar
congresos y reuniones científicas
Título:
Strong Distortion of Saturn's Magnetopause Surface Observed by Cassini
Autor/es:
ACHILLEOS, N.; ARRIDGE, C. S.; BERTUCCI, C.; MCANDREWS, H. J.; DOUGHERTY, M. K.; COATES, A. J.; TEAM, C. M.
Reunión:
Congreso; AGU Fall Meeting 2006; 2006
Resumen:
The Cassini spacecraft has now encountered Saturn's magnetopause
boundary many times, over more than 20 orbits of the planet. During the
compilation of minimum variance analyses for the inbound 'Rev 5' orbit
(March 2005), we have detected what appears to be a significantly
'distorted' orientation of the magnetopause for the final pair of
crossings on the inbound leg. This pair of crossings encloses a brief
(~10 minute) excursion into the planetary magnetosheath (as revealed by
the CAPS instrument), which occurred an unusually long time (>6
hours) and distance (3 RS = Saturn radii) after the earlier group of at
least seven clear magnetopause encounters. Application of an equilibrium
magnetopause model indicates that the standoff distance changed from ~20
to ~17 RS during this time interval and that the model solar wind
pressure correspondingly changed by a factor of nearly two. Therefore, a
strong magnetospheric compression is indicated. Minimum variance
analysis (MVA) reveals that all the crossings correspond to a tangential
discontinuity. Moreover, the angle between the MVA and model normals is
in the range 10-35 deg for the early group of encounters, but increases
to 50-60 deg for the pair associated with the compressed configuration.
The magnetic data acquired by the MAG instrument show that the field
during the brief (~10 min) magnetosheath excursion associated with the
compression reached orientations nearly orthogonal to a model of the
unperturbed magnetopause surface. The observations are consistent with a
sharp 'depression' in the magnetopause surface with a sunward component
of motion. If an anti-sunward moving disturbance is assumed, then we
require an even more distorted, 'folded' magnetopause in order to
explain the observations.