Tidal Response of Preliminary Jupiter Model

Abstract

In anticipation of improved observational data for Jupiter's gravitational field from the Juno spacecraft, we predict the static tidal response for a variety of Jupiter interior models based on ab initio computer simulations of hydrogen-helium mixtures. We calculate hydrostatic-equilibrium gravity terms using the non-perturbative concentric Maclaurin Spheroid (CMS) method that eliminates lengthy expansions used in the theory of figures. Our method captures terms arising from the coupled tidal and rotational perturbations, which we find to be important for a rapidly-rotating planet like Jupiter. Our predicted static tidal Love number $k_2 = 0.5900$ is $\sim$10\% larger than previous estimates. The value is, as expected, highly correlated with the zonal harmonic coefficient $J_2$, and is thus nearly constant when plausible changes are made to interior structure while holding $J_2$ fixed at the observed value. We note that the predicted static $k_2$ might change due to Jupiter's dynamical response to the Galilean moons, and find reasons to argue that the change may be detectable, although we do not present here a theory of dynamical tides for highly oblate Jovian planets. An accurate model of Jupiter's tidal response will be essential for interpreting Juno observations and identifying tidal signals from effects of other interior dynamics in Jupiter's gravitational field.