1203.3867 (Benoît Noyelles)

The rotation of Io predicted by the Poincaré-Hough model    [PDF]

Benoît Noyelles

This paper proposes to study the rotation of the Galilean satellite of Jupiter Io, in considering core-mantle coupling. This satellite is particularly interesting because it experiences strong tidal dissipation inducing a very active surface. Moreover, the flow of the fluid inside its core is reputed to be unstable. We first elaborate 10 different models of the interior of Io, considering either a Fe or a FeS core, using measured values of the gravity coefficients J2 and C22, before studying their response to the 4-degrees of freedom Poincar\'e-Hough model. The study requires numerical methods like integration of ODE and frequency analysis of the solutions. We then study the stability of the flow of the fluid. We show that these different models have a quite small influence on the longitudinal librations and the equilibrium obliquity, with amplitude of about 30 and 8 seconds of arc respectively, because of the relatively small inertia of the core. However, sulfur in the core can pump the tilt of the velocity field constituting the core. Moreover, in all our models the flow in unstable with a growth time of about 1,000 years for a Fe core and 5,000 years for a FeS one.

View original: http://arxiv.org/abs/1203.3867