INERTIAL WAVES IN A LABORATORY MODEL OF THE

A water-filled three-meter diameter spherical shell built as a model of the Earth’s core shows evidence of precessionally forced flows and, when spinning the inner sphere differentially, inertial modes are excited. We identified the precession-ally forced flow to be primarily the spin-over inertial mode, i.e., a uniform vorticity flow whose rotation axis is not aligned with the container’s rotation axis. A sys-tematic study of the spin-over mode is carried out, showing that the amplitude dependence on the Poincare ́ number is in qualitative agreement with Busse’s lami-nar theory while its phase differs significantly, likely due to topographic effects. At high rotation rates free shear layers concentrating most of the kinetic energy of the spin-over mode have been observed. When spinning the inner sphere differentially, a total of 12 inertial modes have been identified, reproducing and extending previous experimental results. The inertial modes excited appear ordered according to thei