Dynamics and Chaotic Long-Term Diffusion of Jovian Irregular Satellites - Implications for…

The dynamical time evolution of Jovian irregular satellites is mainly governed by solar and giant planet gravitational perturbations and the satellite orbits are expected to exhibit chaotic dynamics to some degree. Usually chaotic motion arises from the existence of nearby orbital resonances (i.e mean-motion, evection, secular and Kozai-Lidov resonances) and their possible overlap, which results in changes in the satellite's proper elements under angular momentum exchange. For the retrograde Jovian satellites several clusters have been identified, most likely pointing at a past collision history. At current time a kinematic conundrum exists: These clusters exhibit an excess in their observed velocity dispersion. To reconcile their observed velocity fields with laboratory and hydro-code experiments on the fragmentation of small bodies, an additional dynamical mechanism is required to further disperse a post-collision satellite cloud. We have applied the MEGNO technique to map the locations of solar mean-motion resonances and planetary secular resonances in the vicinity of retrograde satellites. These have been followed up with long-term numerical integrations of synthetic satellite clusters to ascertain whether these resonances can introduce sufficient orbital dispersion to explain the observed retrograde orbital distribution. Fundamental irregular satellite dynamics and the results of our experiments will be presented and the possible use of irregular satellite studies to test giant planet formation history is discussed.