a much more important impact on the dynamical evolution.

As Fig. \[MS-Hr\] shows, if the aspect ratio is small (3 – 4%), the evolution is similar to that previously considered. When released, Jupiter starts to migrate outward, while Saturn moves inward. After locking in the mutual 2:3 mean motion resonance, both planets move outward. In these cases, the migration is indeed faster if the disk is thinner, as found in MS01. However, for thicker disks, the evolution changes qualitatively. If the aspect ratio is 5%, we find a quasi-stationary solution. After locking in the 2:3 MMR, both Jupiter and Saturn essentially do not migrate any more. [Actually, Jupiter moves outward by only 1.5% in 2000 orbits]{}. To our knowledge, this is the first quasi-stationary solution ever found for a system of giant planets in a fully evolving disk. If the disk thickness is increased to 6%, both planets migrate inward, even after being captured into the 2:3 MMR. This migration is very slow, compared to that of an isolated Jupiter in the same disk. This sequence of behaviours relative to aspect ratio also suggests that, in a flaring disk, the planets might migrate until they find a position in the 