Numerical study of librationally driven Fow in planetary interiors

Forced librations are observed for many planetary bodies. In the case of interior fluid layers, i.e. liquid cores or subsurface oceans, the resulting librational response could be different compared to that of a solid body. The coupling between the fluid layer and mantle depends strongly on the interior properties of the planet. Here we study numerically the properties of a librationally driven flow by taking into account both longitudinal and latitudinal forcing. The numerical method is based on a finite element approximation in meridian planes and a Fourier decomposition of the variables in the azimuthal direction (SFEMANS, Spectral Finite Element for Maxwell and Navier Stokes). This allows us to specify the direction of rotation vector arbitrarily. In the case of longitudinal forcing we compare our solutions to the experimental results of Noir et al. 2009 and Calkins et al. 2009 (see poster "Modeling Subsurface Flows Driven by Planetary Libration" in this session) obtained for cores with spherical shape. For latitudinal librations, we consider also the influence of ellipticity.